Mécanismes de défense

Agarrwal, R., Padmakumari, A. P., Bentur, J. S., & Nair, S. (2016). Metabolic and

transcriptomic changes induced in host during hypersensitive response mediated

resistance in rice against the Asian rice gall midge. Rice, 9(1), 1‑15.

https://doi.org/10.1186/s12284-016-0077-6

Background An incompatible interaction between rice (Oryza sativa) and the Asian rice

gall midge (AGM, Orseolia oryzae Wood-Mason), that is usually manifested through a

hypersensitive response (HR), represents an intricate relationship between the resistant

host and its avirulent pest. We investigated changes in the transcriptome and

metabolome of the host (indica rice variety: RP2068-18-3-5, RP), showing HR when

attacked by an avirulent gall midge biotype (GMB1), to deduce molecular and

biochemical bases of such a complex interaction. Till now, such an integrated analysis of

host transcriptome and metabolome has not been reported for any rice-insect

interaction. Results Transcript and metabolic profiling data revealed more than 7000

differentially expressed genes and 80 differentially accumulated metabolites,

respectively, in the resistant host. Microarray data revealed deregulation of carbon (C)

and nitrogen (N) metabolism causing a C/N shift; up-regulation of tetrapyrrole synthesis

and down-regulation of chlorophyll synthesis and photosynthesis. Integrated results

revealed that genes involved in lipid peroxidation (LPO) were up-regulated and a marker

metabolite for LPO (azelaic acid) accumulated during HR. This coincided with a greater

accumulation of GABA (neurotransmitter and an insect antifeedant) at the feeding site.

Validation of microarray results by semi-quantitative RT-PCR revealed temporal variation

in gene expression profiles. Conclusions The study revealed extensive reprogramming of

the transcriptome and metabolome of RP upon GMB1 infestation leading to an HR that

was induced by the generation and release of reactive oxygen species i.e. singlet oxygen

and resulted in LPO-mediated cell death. RP thus used HR as a means to limit nutrient

supply to the feeding maggots and simultaneously accumulated GABA, strategies that

could have led to maggot mortality. The integrated results of transcript and metabolic

profiling, for the first time, provided insights into an HR+ type of resistance in rice

against gall midge.

An, C., Ding, Y., Zhang, X., Wang, C., & Mou, Z. (2016). Elongator Plays a Positive Role

in Exogenous Nicotinamide Adenine Dinucleotide-Induced Defense Responses in

Arabidopsis. Molecular Plant-Microbe Interactions: MPMI. https://doi.org/10.1094/MPMI-

01-16-0005-R

Extracellular nicotinamide adenine dinucleotide (eNAD) is emerging as an important

signal molecule in animal cells, but its role in plants has not been well established.

Although it has been shown that exogenous NAD+ activates defense responses in

Arabidopsis, components in the exogenous NAD+-activated defense pathway remain to

be fully uncovered. In a genetic screen for mutants insensitive to exogenous NAD+ (ien),

we isolated a mutant named ien2. Map-based cloning revealed that IEN2 encodes

ELONGATA3 (ELO3)/AtELP3, a subunit of the Arabidopsis Elongator complex, which

functions in multiple biological processes including histone modification, DNA

(de)methylation, and tRNA modification. Mutations in the ELO3/AtELP3 gene compromise

exogenous NAD+-induced expression of PATHOGENESIS-RELATED (PR) genes and

resistance to the bacterial pathogen Pseudomonas syringae pv maculicola (Psm) ES4326,

and transgenic expression of the coding region of ELO3/AtELP3 in elo3/Atelp3 restores

NAD+ responsiveness to the mutant plants, demonstrating that ELO3/AtELP3 is required

for exogenous NAD+-induced defense responses. Furthermore, mutations in genes

encoding the other five Arabidopsis Elongator subunits (ELO2/AtELP1, AtELP2,

ELO1/AtELP4, AtELP5, and AtELP6) also compromise exogenous NAD+-induced PR gene

expression and resistance to Psm ES4326. These results indicate that the Elongator

complex functions as a whole in exogenous NAD+-activated defense signaling in

Arabidopsis.

Cheol Song, G., Sim, H. J., Kim, S. G., & Ryu, C. M. (2016). Root-mediated signal

transmission of systemic acquired resistance against above-ground and below-ground

pathogens. Annals of Botany. https://doi.org/10.1093/aob/mcw152

BACKGROUND AND AIMS: Plants modulate defence signalling networks in response to

various biotic stresses via inter-organ communications. The root-mediated transmission

of systemic acquired resistance (SAR) against soil-borne and air-borne plant pathogens

from SAR-induced plants to neighbouring plants subjected to local chemical and

pathogen treatments was evaluated.METHODS: The first two plants out of ten Nicotiana

benthamiana seedlings were pre-treated with the SAR-triggering chemical

benzothiadiazole (BTH). All ten seedlings were then challenged with two pathogenic

bacteria, i.e. the root (bacterial wilt) pathogen Ralstonia solanacearum and the leaf

(wildfire) pathogen Pseudomonas syringae pv. tabaci, at 7 d after SAR induction.KEY

RESULTS: Disease severity was noticeably lower in BTH-pre-treated plants than in the

control. Surprisingly, two plants located next to BTH-treated plants exhibited reduced

disease symptoms indicating that SAR signal transmission occurred through the root

system. Determinant(s) secreted from the root system were search for and it was found

that salicylic acid (SA) is a major molecule involved in SAR transmission through the

root. Analysis of the expression of the defence-related genes N. benthamiana

pathogenesis-related gene 1a (NbPR1a) and NbPR2 confirmed that BTH treatment

elicited SAR via root-root transmission between plants. Plants with knock-down of the

multiple resistance component SGT1 and SA biosynthesis-related gene ICS1 by Tobacco

rattle virus-mediated virus-induced gene silencing exhibited a lack of root-mediated SAR

transmission. The biological relevance of this finding was validated by challenge with the

SAR-inducing avirulent pathogen P. syringae pv. syringae instead of BTH, which produced

similar results.CONCLUSIONS: Our findings demonstrated that SAR is transmissible

through the root system from SAR-triggered plants to neighbouring plants.

Choi, H. W., Manohar, M., Manosalva, P., Tian, M., Moreau, M., & Klessig, D. F. (2016).

Activation of Plant Innate Immunity by Extracellular High Mobility Group Box 3 and Its

Inhibition by Salicylic Acid. PLOS Pathog, 12(3), e1005518.

https://doi.org/10.1371/journal.ppat.1005518

In mammals, extracellular HMGB1 is the prototypic Damage-Associated Molecular Pattern

(DAMP) molecule, which activates inflammatory and immune responses to protect

against infection and promote healing after tissue damage. Increasing evidence argues

that it also plays important roles in many diseases. In contrast, the role of HMGB

proteins in plant immunity has not been reported. We recently identified human HMGB1

as a novel Salicylic Acid-Binding Protein (SABP) and found that its DAMP activities are

specifically inhibited by SA binding. In this study, we showed that i) infection by a

necrotrophic pathogen releases plant HMGB3 into the apoplast, ii) extracellular, HMGB3

activates immune responses, iii) SA binds to HMGB3, and iv) this binding alters its DAMP

activity. These findings provide the first demonstration that a plant HMGB function as a

DAMP, like its human counterpart, as well as the insights into how SA inhibits both plant

and animal HMGB-induced immunity.

Gramegna, G., Modesti, V., Savatin, D. V., Sicilia, F., Cervone, F., & De Lorenzo, G.

(2016). GRP-3 and KAPP, encoding interactors of WAK1, negatively affect defense

Gravino, M., Locci, F., Tundo, S., Cervone, F., Valentin Savatin, D., & De Lorenzo, G.

(2016). Immune responses induced by oligogalacturonides are differentially affected by

AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2. Molecular Plant Pathology, n/a-n/a.

https://doi.org/10.1111/mpp.12419

Plants possess an innate immune system capable of restricting invasion by most potential

pathogens. At the cell surface, recognition of microbe-associated molecular patterns

(MAMPs) and/or damage-associated molecular patterns (DAMPs) by pattern recognition

receptors (PRRs) represents the first event for promptly mounting an effective immune

response. Pathogens have evolved effectors that block MAMP-triggered immunity. The

Pseudomonas syringae effector AvrPto abolishes immunity triggered by the peptide

MAMPs flg22 and elf18, derived from the bacterial flagellin and Elongation factor Tu,

respectively, by inhibiting the kinase function of the corresponding receptors FLS2 and

EFR, as well as of their co-receptors BAK1 and BKK1. Oligogalacturonides (OGs), a well-

known class of DAMPs, are oligomers of alpha-1,4-linked galacturonosyl residues

released upon partial degradation of the plant cell wall homogalacturonan. We show here

that AvrPto affects only a subset of the OG-triggered immune responses and that, among

these responses, only a subset is affected by the concomitant loss of BAK1 and BKK1. On

the other hand, the antagonistic effect on auxin-related responses is not affected by

either AvrPto or the loss of BAK1/BKK1. These observations reveal an unprecedented

complexity among the MAMP/DAMP response cascades. We also show that the signaling

system mediated by Peps, another class of DAMPs, and their receptors PEPRs,

contributes to OG-activated immunity. We hypothesize that OGs are sensed through

multiple and partially redundant perception/transduction complexes, some targeted by

AvrPto but not necessarily comprise BAK1 and BKK1.

Asha, S., & Soniya, E. V. (2016). Transfer RNA Derived Small RNAs Targeting Defense

Responsive Genes Are Induced during Phytophthora capsici Infection in Black Pepper

(Piper nigrum L.). Frontiers in Plant Science, 7, 767.

https://doi.org/10.3389/fpls.2016.00767

Small RNAs derived from transfer RNAs were recently assigned as potential gene

regulatory candidates for various stress responses in eukaryotes. In this study, we report

on the cloning and identification of tRNA derived small RNAs from black pepper plants in

response to the infection of the quick wilt pathogen, Phytophthora capsici. 5’tRFs cloned

from black pepper were validated as highly expressed during P. capsici infection. A high-

throughput systematic analysis of the small RNAome (sRNAome) revealed the

predominance of 5’tRFs in the infected leaf and root. The abundance of 5’tRFs in the

sRNAome and the defense responsive genes as their potential targets indicated their

regulatory role during stress response in black pepper. The 5’Ala(CGC) tRF mediated

cleavage was experimentally mapped at the tRF binding sites on the mRNA targets of

Non-expresser of pathogenesis related protein (NPR1), which was down-regulated during

pathogen infection. Comparative sRNAome further demonstrated sequence conservation

of 5’Ala tRFs across the angiosperm plant groups, and many important genes in the

defense response were identified in silico as their potential targets. Our findings

uncovered the diversity, differential expression and stress responsive functional role of

tRNA-derived small RNAs during Phytophthora infection in black pepper.

Balagué, C., Gouget, A., Bouchez, O., Souriac, C., Haget, N., Boutet-Mercey, S., …

Canut, H. (2016). The Arabidopsis thaliana lectin receptor kinase LecRK-I.9 is required

for full resistance to Pseudomonas syringae and affects jasmonate signalling. Molecular

Plant Pathology. https://doi.org/10.1111/mpp.12457

Upon microbial attack, plants can detect the invaders and activate the plant innate

immunity system. For detecting pathogen molecules or cell wall damage, plants employ

receptors that trigger the activation of defence responses. Cell surface proteins that

belong to large families of lectin receptor kinases are candidates to function as immune

receptors. Here the function of LecRK-I.9 (At5g60300), a legume-type lectin receptor

kinase involved in cell wall - plasma membrane contacts and in eATP perception, was

studied through biochemical, gene expression and reverse genetics approaches. In

Arabidopsis thaliana, LecRK-I.9 expression is rapidly, highly and locally induced upon

inoculation with avirulent strains of Pseudomonas syringae pv. tomato (Pst). Two allelic

lecrk-I.9 knock-out mutants showed decreased resistance to Pst. Conversely, over-

expression of LecRK-I.9 led to increased resistance to Pst. Analysis of defence gene

expression suggests an alteration of both the salicylic acid (SA) and the jasmonic acid

(JA) signalling pathways. In particular, LecRK-I.9 expression during the plant-pathogen

interaction was dependent on COI-1 and JAR-1 components and JA-responsive

transcription factors (TFs) showed altered levels of expression in plants over-expressing

LecRK-I.9. A similar misregulation of these TFs was obtained by JA treatment. This study

identified LecRK-I.9 as necessary for full resistance to Pst and pointed out its

involvement in the control of defence towards pathogens through a regulation of JA

signalling components. The role of LecRK-I.9 is discussed with regard to the potential

molecular mechanisms linking JA signalling to cell wall damages and/or eATP perception.

This article is protected by copyright.

Biswas, M. S., & Mano, J. (2016). Reactive Carbonyl Species Activate Caspase-3-Like

Protease to Initiate Programmed Cell Death in Plants. Plant and Cell Physiology, 57(7),

1432‑1442. https://doi.org/10.1093/pcp/pcw053

Reactive oxygen species (ROS)-triggered programmed cell death (PCD) is a typical plant

response to biotic and abiotic stressors. We have recently shown that lipid peroxide-

derived reactive carbonyl species (RCS), downstream products of ROS, mediate oxidative

signal to initiate PCD. Here we investigated the mechanism by which RCS initiate PCD.

Tobacco Bright Yellow-2 cultured cells were treated with acrolein, one of the most potent

RCS. Acrolein at 0.2 mM caused PCD in 5 h (i.e. lethal), but at 0.1 mM it did not

(sublethal). Specifically, these two doses caused critically different effects on the cells.

Both lethal and sublethal doses of acrolein exhausted the cellular glutathione pool in 30

min, while the lethal dose only caused a significant ascorbate decrease and ROS increase

in 1–2 h. Prior to such redox changes, we found that acrolein caused significant increases

in the activities of caspase-1-like protease (C1LP) and caspase-3-like protease (C3LP),

the proteases which trigger PCD. The lethal dose of acrolein increased the C3LP activity

2-fold more than did the sublethal dose. In contrast, C1LP activity increments caused by

the two doses were not different. Acrolein and 4-hydroxy-(E)-2-nonenal, another RCS,

activated both proteases in a cell-free extract from untreated cells. H2O2 at 1 mM added

to the cells increased C1LP and C3LP activities and caused PCD, and the RCS scavenger

carnosine suppressed their activation and PCD. However, H2O2 did not activate the

proteases in a cell-free extract. Thus the activation of caspase-like proteases, particularly

C3LP, by RCS is an initial biochemical event in oxidative signal-stimulated PCD in plants.

Brauer, E. K., Ahsan, N., Dale, R., Kato, N., Coluccio, A. E., Piñeros, M. A., … Popescu, S.

C. (2016). The Raf-like Kinase ILK1 and the High Affinity K+ Transporter HAK5 Are

Required for Innate Immunity and Abiotic Stress Response. Plant Physiology, 171(2),

1470‑1484. https://doi.org/10.1104/pp.16.00035

Plant perception of pathogen-associated molecular patterns (PAMPs) and other

environmental stresses trigger transient ion fluxes at the plasma membrane. Apart from

the role of Ca2+ uptake in signaling, the regulation and significance of PAMP-induced ion

fluxes in immunity remain unknown. We characterized the functions of INTEGRIN-LINKED

KINASE1 (ILK1) that encodes a Raf-like MAP2K kinase with functions insufficiently

understood in plants. Analysis of ILK1 mutants impaired in the expression or kinase

activity revealed that ILK1 contributes to plant defense to bacterial pathogens, osmotic

stress sensitivity, and cellular responses and total ion accumulation in the plant upon

treatment with a bacterial-derived PAMP, flg22. The calmodulin-like protein CML9, a

negative modulator of flg22-triggered immunity, interacted with, and suppressed ILK1

kinase activity. ILK1 interacted with and promoted the accumulation of HAK5, a putative

(H+)/K+ symporter that mediates a high-affinity uptake during K+ deficiency. ILK1 or

HAK5 expression was required for several flg22 responses including gene induction,

growth arrest, and plasma membrane depolarization. Furthermore, flg22 treatment

induced a rapid K+ efflux at both the plant and cellular levels in wild type, while mutants

with impaired ILK1 or HAK5 expression exhibited a comparatively increased K+ loss.

Taken together, our results position ILK1 as a link between plant defense pathways and

K+ homeostasis.

Camejo, D., Guzmán-Cedeño, Á., & Moreno, A. (2016). Reactive oxygen species,

essential molecules, during plant–pathogen interactions. Plant Physiology and

Biochemistry, 103, 10‑23. https://doi.org/10.1016/j.plaphy.2016.02.035

Reactive oxygen species (ROS) are continually generated as a consequence of the normal

metabolism in aerobic organisms. Accumulation and release of ROS into cell take place in

response to a wide variety of adverse environmental conditions including salt,

temperature, cold stresses and pathogen attack, among others. In plants, peroxidases

class III, NADPH oxidase (NOX) locates in cell wall and plasma membrane, respectively,

may be mainly enzymatic systems involving ROS generation. It is well documented that

ROS play a dual role into cells, acting as important signal transduction molecules and as

toxic molecules with strong oxidant power, however some aspects related to its function

during plant-pathogen interactions remain unclear. This review focuses on the principal

enzymatic systems involving ROS generation addressing the role of ROS as signal

molecules during plant-pathogen interactions. We described how the chloroplasts,

mitochondria and peroxisomes perceive the external stimuli as pathogen invasion, and

trigger resistance response using ROS as signal molecule.

Cao, J. Y., Xu, Y. P., & Cai, X. Z. (2016). TMT-based quantitative proteomics analyses

reveal novel defense mechanisms of Brassica napus against the devastating necrotrophic

pathogen Sclerotinia sclerotiorum. Journal of Proteomics.

https://doi.org/10.1016/j.jprot.2016.03.006

The white mould disease, caused by Sclerotinia sclerotiorum, is one of the most

important diseases in the vital oil crop Brassica napus. Nevertheless, the defense

mechanisms of B. napus against S. sclerotiorum are poorly understood. In this study, we

performed comparative quantitative proteomics analyses to reveal B. napus defense

mechanisms against S. sclerotiorum. The proteomes of B. napus leaves inoculated with

S. sclerotiorum wild-type strain 1980 and nonpathogenic mutant strain Ep-1PB as well as

empty agar plug as the control were analyzed using TMT label-based quantitative

analysis technique. A total of 79, 299 and 173 proteins consistently differentially

expressed between Ep-1PB- and mock-inoculated leaves, 1980- and mock-inoculated

leaves, as well as 1980- and Ep-1PB-inoculated leaves, respectively, were identified. The

differential expression of 12 selected proteins was confirmed by qRT-PCR analyses. The

Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-

protein interaction prediction analyses revealed that redox homeostasis, lipid signaling,

calcium signaling, histone and DNA methylation-mediated transcription regulation and

defense-related proteins such as defensin and defensin-like proteins and cyanate lyase,

contribute to defense against S. sclerotiorum. Our results provide new insights into

molecular mechanisms that may be involved in defense responses of B. napus to S.

sclerotiorum.SIGNIFICANCE: The Sclerotinia white mould disease is one of the most

important diseases in the significant oil crop Brassica napus. Nevertheless, the defense

mechanisms of B. napus against S. sclerotiorum are still largely unknown to date. In this

study, we addressed this issue by performing TMT label-based comparative quantitative

analyses of the proteomes of B. napus leaves inoculated with S. sclerotiorum wild-type

strain 1980 and nonpathogenic mutant strain Ep-1PB as well as empty agar plug as the

control. Through comparative analyses on 79, 299, and 173 proteins that are consistently

differentially expressed in between Ep-1PB-inoculated and the control leaves, 1980-

inoculated and the control leaves, as well as 1980-inoculated and Ep-1PB-inoculated

leaves, respectively, we revealed that redox homeostasis, lipid signaling, calcium

signaling, histone and DNA methylation-mediated transcription regulation and defense-

related proteins such as defensin and defensin-like proteins as well as cyanate lyase,

contribute to B. napus defenses against S. sclerotiorum. Notably, the potential role of

lipid signaling, calcium signaling, histone and DNA methylation-mediated transcription

regulation and cyanate lyase in B. napus defense against S. sclerotiorum are not

reported previously but rather unveiled for the first time in this study. The current study

represents the most extensive analysis of the protein profile of B. napus in response to S.

sclerotiorum inoculation and includes for the first time the results from comparison

between plants inoculated with the wild-type strain and a nonpathogenic mutant strain of

S. sclerotiorum. Collectively, our results provide new insights into the molecular

mechanisms of interactions between B. napus and S. sclerotiorum.

Chakraborty, S., Nascimento, R., Zaini, P. A., Gouran, H., Rao, B. J., Goulart, L. R., &

Dandekar, A. M. (2016). Sequence/structural analysis of xylem proteome emphasizes

pathogenesis-related proteins, chitinases and β-1, 3-glucanases as key players in

grapevine defense against Xylella fastidiosa. PeerJ, 4, e2007.

https://doi.org/10.7717/peerj.2007

Background. Xylella fastidiosa, the causative agent of various plant diseases including

Pierce’s disease in the US, and Citrus Variegated Chlorosis in Brazil, remains a continual

source of concern and economic losses, especially since almost all commercial varieties

are sensitive to this Gammaproteobacteria. Differential expression of proteins in infected

tissue is an established methodology to identify key elements involved in plant defense

pathways. Methods. In the current work, we developed a methodology named CHURNER

that emphasizes relevant protein functions from proteomic data, based on identification

of proteins with similar structures that do not necessarily have sequence homology. Such

clustering emphasizes protein functions which have multiple copies that are up/down-

regulated, and highlights similar proteins which are differentially regulated. As a working

example we present proteomic data enumerating differentially expressed proteins in

xylem sap from grapevines that were infected with X. fastidiosa. Results. Analysis of this

data by CHURNER highlighted pathogenesis related PR-1 proteins, reinforcing this as the

foremost protein function in xylem sap involved in the grapevine defense response to X.

fastidiosa. β-1, 3-glucanase, which has both anti-microbial and anti-fungal activities, is

also up-regulated. Simultaneously, chitinases are found to be both up and down-

regulated by CHURNER, and thus the net gain of this protein function loses its

significance in the defense response. Discussion. We demonstrate how structural data

can be incorporated in the pipeline of proteomic data analysis prior to making inferences

on the importance of individual proteins to plant defense mechanisms. We expect

CHURNER to be applicable to any proteomic data set.

Chaloner, T., Van Kan, J. A. L., & Grant-Downton, R. T. (2016). RNA ‘Information

Warfare’ in Pathogenic and Mutualistic Interactions. Trends in Plant Science, 0(0).

https://doi.org/10.1016/j.tplants.2016.05.008

Regulatory non-coding RNAs are emerging as key players in host–pathogen interactions.

Small RNAs such as microRNAs are implicated in regulating plant transcripts involved in

immunity and defence. Surprisingly, RNAs with silencing properties can be translocated

from plant hosts to various invading pathogens and pests. Small RNAs are now confirmed

virulence factors, with the first report of fungal RNAs that travel to host cells and hijack

post-transcriptional regulatory machinery to suppress host defence. Here, we argue that

trans-organism movement of RNAs represents a common mechanism of control in

diverse interactions between plants and other eukaryotes. We suggest that extracellular

vesicles are the key to such RNA movement events. Plant pathosystems serve as

excellent experimental models to dissect RNA ‘information warfare’ and other RNA-

mediated interactions., Plant–pathogen interactions have undergone a paradigm shift,

with the observation that silencing, non-coding RNAs move between host and pathogen,

and vice versa., So far, only one unequivocal natural example of this phenomenon has

been exposed, where RNAs from Botrytis cinerea (grey mould) move into host plants.

There, they ‘hijack’ host silencing machinery to downregulate transcripts involved in

defence and immunity., Similar RNA-based phenomena in interactions between animals

and their microbial pathogens suggest that this mechanism is a commonality between

infections in widely divergent taxa., As well as a potent tool for developing new crops

with increased disease resistance, studies of RNA traffic between plants and their

symbionts will serve as models for other disease interactions.

Corwin, J. A., Copeland, D., Feusier, J., Subedy, A., Eshbaugh, R., Palmer, C., …

Kliebenstein, D. J. (2016). The Quantitative Basis of the Arabidopsis Innate Immune

System to Endemic Pathogens Depends on Pathogen Genetics. PLoS Genetics, 12(2),

e1005789. https://doi.org/10.1371/journal.pgen.1005789

The most established model of the eukaryotic innate immune system is derived from

examples of large effect monogenic quantitative resistance to pathogens. However, many

host-pathogen interactions involve many genes of small to medium effect and exhibit

quantitative resistance. We used the Arabidopsis-Botrytis pathosystem to explore the

quantitative genetic architecture underlying host innate immune system in a population

of Arabidopsis thaliana. By infecting a diverse panel of Arabidopsis accessions with four

phenotypically and genotypically distinct isolates of the fungal necrotroph B. cinerea, we

identified a total of 2,982 genes associated with quantitative resistance using lesion area

and 3,354 genes associated with camalexin production as measures of the interaction.

Most genes were associated with resistance to a specific Botrytis isolate, which

demonstrates the influence of pathogen genetic variation in analyzing host quantitative

resistance. While known resistance genes, such as receptor-like kinases (RLKs) and

nucleotide-binding site leucine-rich repeat proteins (NLRs), were found to be enriched

among associated genes, they only account for a small fraction of the total genes

associated with quantitative resistance. Using publically available co-expression data, we

condensed the quantitative resistance associated genes into co-expressed gene

networks. GO analysis of these networks implicated several biological processes

commonly connected to disease resistance, including defense hormone signaling and ROS

production, as well as novel processes, such as leaf development. Validation of single

gene T-DNA knockouts in a Col-0 background demonstrate a high success rate (60%)

when accounting for differences in environmental and Botrytis genetic variation. This

study shows that the genetic architecture underlying host innate immune system is

extremely complex and is likely able to sense and respond to differential virulence among

pathogen genotypes.

Du, S. C., Lim, C. W., & Hwang, B. K. (2016). Proteomics and functional analyses of

Arabidopsis nitrilases involved in the defense response to microbial pathogens. Planta.

https://doi.org/10.1007/s00425-016-2525-3

MAIN CONCLUSION: Proteomics and functional analyses of the Arabidopsis -

Pseudomonas syringae pv. tomato interactions reveal that Arabidopsis nitrilases are

required for plant defense and R gene-mediated resistant responses to microbial

pathogens. A high-throughput in planta proteome screen has identified Arabidopsis

nitrilase 2 (AtNIT2), which was de novo-induced by Pseudomonas syringae pv. tomato

(Pst) infection. The AtNIT2, AtNIT3, and AtNIT4 genes, but not AtNIT1, were distinctly

induced in Arabidopsis leaves by Pst infection. Notably, avirulent Pst DC3000 (avrRpt2)

infection led to significant induction of AtNIT2 and AtNIT4 in leaves. Pst DC3000 and Pst

DC3000 (avrRpt2) significantly grew well in leaves of nitrilase transgenic (nit2i-2) and

mutant (nit1-1 and nit3-1) lines compared to the wild-type leaves. In contrast, NIT2

overexpression in nit2 mutants led to significantly high growth of the two Pst strains in

leaves. The nitrilase transgenic and mutant lines exhibited enhanced susceptibility to

Hyaloperonospora arabidopsidis infection. The nit2 mutation enhanced Pst DC3000

(avrRpt2) growth in salicylic acid (SA)-deficient NahG transgenic and sid2 and npr1

mutant lines. Infection with Pst DC3000 or Pst DC3000 (avrRpt2) induced lower levels of

indole-3-acetic acid (IAA) in nit2i and nit2i NahG plants than in wild-type plants, but did

not alter the IAA level in NahG transgenic plants. This suggests that Arabidopsis nitrilase

2 is involved in IAA signaling of defense and R gene-mediated resistance responses to Pst

infection. Quantification of SA in these transgenic and mutant plants demonstrates that

Arabidopsis nitrilase 2 is not required for SA-mediated defense response to the virulent

Pst DC3000 but regulates SA-mediated resistance to the avirulent Pst DC3000 (avrRpt2).

These results collectively suggest that Arabidopsis nitrilase genes are involved in plant

defense and R gene-mediated resistant responses to microbial pathogens.

Hatsugai, N., Hillmer, R. A., Yamaoka, S., Hara-Nishimura, I., & Katagiri, F. (2016). The

μ Subunit of Arabidopsis Adaptor Protein-2 Is Involved in Effector-Triggered Immunity

Mediated by Membrane-Localized Resistance Proteins. Molecular Plant-Microbe

Interactions: MPMI. https://doi.org/10.1094/MPMI-10-15-0228-R

Endocytosis has been suggested to be important in the cellular processes of plant

immune responses. However, our understanding of its role during effector-triggered

immunity (ETI) is still limited. We have previously shown that plant endocytosis,

especially clathrin-coated vesicle formation at the plasma membrane, is mediated by the

adaptor protein-2 (AP-2) complex, and that loss of the μ subunit of AP-2 (AP2M) affects

plant growth and floral organ development. Here we report that AP2M is required for full

strength ETI mediated by the disease resistance (R) genes RPM1 and RPS2 in

Arabidopsis. Reduced ETI was observed in an ap2m mutant plant, measured by growth of

Pseudomonas syringae pv. tomato (Pto) DC3000 strains carrying the corresponding

effector genes avrRpm1 or avrRpt2 and by hypersensitive cell death response and

defense gene expression triggered by these strains. In contrast, RPS4-mediated ETI and

its associated immune responses were not affected by the ap2m mutation. While RPM1

and RPS2 are localized to the plasma-membrane, RPS4 is localized to the cytoplasm and

nucleus. Our results suggest that AP2M is involved in ETI mediated by plasma

membrane-localized R proteins, possibly by mediating endocytosis of the immune

receptor complex components from the plasma membrane.

Hawes, M., Allen, C., Turgeon, B. G., Curlango-Rivera, G., Minh Tran, T., Huskey, D. A.,

& Xiong, Z. (2016). Root Border Cells and Their Role in Plant Defense. Annual Review of

Phytopathology. https://doi.org/10.1146/annurev-phyto-080615-100140

Root border cells separate from plant root tips and disperse into the soil environment. In

most species, each root tip can produce thousands of metabolically active cells daily, with

specialized patterns of gene expression. Their function has been an enduring mystery.

Recent studies suggest that border cells operate in a manner similar to mammalian

neutrophils: Both cell types export a complex of extracellular DNA (exDNA) and

antimicrobial proteins that neutralize threats by trapping pathogens and thereby

preventing invasion of host tissues. Extracellular DNases (exDNases) of pathogens

promote virulence and systemic spread of the microbes. In plants, adding DNase I to root

tips eliminates border cell extracellular traps and abolishes root tip resistance to

infection. Mutation of genes encoding exDNase activity in plant-pathogenic bacteria

(Ralstonia solanacearum) and fungi (Cochliobolus heterostrophus) results in reduced

virulence. The study of exDNase activities in plant pathogens may yield new targets for

disease control. Expected final online publication date for the Annual Review of

Phytopathology Volume 54 is August 04, 2016. Please see

http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Heitz, T., Smirnova, E., Widemann, E., Aubert, Y., Pinot, F., & Ménard, R. (2016). The

Rise and Fall of Jasmonate Biological Activities. Sub-Cellular Biochemistry, 86, 405‑426.

https://doi.org/10.1007/978-3-319-25979-6_16

Jasmonates (JAs) constitute a major class of plant regulators that coordinate responses

to biotic and abiotic threats and important aspects of plant development. The core

biosynthetic pathway converts linolenic acid released from plastid membrane lipids to the

cyclopentenone cis-oxo-phytodienoic acid (OPDA) that is further reduced and shortened

to jasmonic acid (JA) in peroxisomes. Abundant pools of OPDA esterified to plastid lipids

also occur upon stress, mainly in the Arabidopsis genus. Long thought to be the bioactive

hormone, JA only gains its pleiotropic hormonal properties upon conjugation into

jasmonoyl-isoleucine (JA-Ile). The signaling pathway triggered when JA-Ile promotes the

assembly of COI1-JAZ (Coronatine Insensitive 1-JAsmonate Zim domain) co-receptor

complexes has been the focus of most recent research in the jasmonate field. In parallel,

OPDA and several other JA derivatives are recognized for their separate activities and

contribute to the diversity of jasmonate action in plant physiology. We summarize in this

chapter the properties of different bioactive JAs and review elements known for their

perception and signal transduction. Much progress has also been gained on the

enzymatic processes governing JA-Ile removal. Two JA-Ile catabolic pathways, operating

through ω-oxidation (cytochromes P450) or conjugate cleavage (amido hydrolases)

shape signal dynamics to allow optimal control on defense. JA-Ile turnover not only

participates in signal attenuation, but also impact the homeostasis of the entire JA

metabolic pathway.

Hiruma, K., & Saijo, Y. (2016). Tracing Plant Defense Responses in Roots upon

MAMP/DAMP Treatment. Methods in Molecular Biology (Clifton, N.J.), 1398, 319‑322.

https://doi.org/10.1007/978-1-4939-3356-3_25

This chapter describes how to apply microbe-associated molecular pattern (MAMP) or

damage-associated molecular pattern (DAMP) solutions to Arabidopsis roots to trace

defense responses in the root. Plants sense the presence of microbes via the perception

of MAMPs or DAMPs by surface-localized pattern recognition receptors. The mechanisms

governing plant root immunity are poorly characterized compared with those underlying

plant immunity in the leaf, despite the fact that plant roots constantly interact with

countless microbes living in soils that carry potential MAMPs and could stimulate the

production of plant-derived DAMPs during colonization. To understand how a plant root

immune system detects and reacts to the potential sources of a stimulus, we describe a

simple method to monitor activation of root immunity upon MAMP/DAMP treatment by

measuring relative expression of defense-related genes by RT-qPCR.

Jia, X., Meng, Q., Zeng, H., Wang, W., & Yin, H. (2016). Chitosan oligosaccharide induces

resistance to Tobacco mosaic virus in Arabidopsis via the salicylic acid-mediated

signalling pathway. Scientific Reports, 6, 26144. https://doi.org/10.1038/srep26144

Chitosan is one of the most abundant carbohydrate biopolymers in the world, and

chitosan oligosaccharide (COS), which is prepared from chitosan, is a plant immunity

regulator. The present study aimed to validate the effect of COS on inducing resistance

to tobacco mosaic virus (TMV) in Arabidopsis and to investigate the potential defence-

related signalling pathways involved. Optimal conditions for the induction of TMV resistance in Arabidopsis were COS pretreatment at 50 mg/L for 1 day prior to inoculation

with TMV. Multilevel indices, including phenotype data, and TMV coat protein expression,

revealed that COS induced TMV resistance in wild-type and jasmonic acid pathway-

deficient (jar1) Arabidopsis plants, but not in salicylic acid pathway deficient (NahG)

Arabidopsis plants. Quantitative-PCR and analysis of phytohormone levels confirmed that

COS pretreatment enhanced the expression of the defence-related gene PR1, which is a

marker of salicylic acid signalling pathway, and increased the amount of salicylic acid in

WT and jar1, but not in NahG plants. Taken together, these results confirm that COS

induces TMV resistance in Arabidopsis via activation of the salicylic acid signalling

pathway.

Jiang, Y., & Yu, D. (2016). WRKY57 regulates JAZ genes transcriptionally to compromise

Botrytis cinerea resistance in Arabidopsis thaliana. Plant Physiology.

https://doi.org/10.1104/pp.16.00747

Although necrotrophic pathogens cause many devastating plant diseases, our

understanding of the plant defense response to them is limited. Here, we found that loss

of function of WRKY57 enhanced the resistance of Arabidopsis thaliana against Botrytis

cinerea infection. Further investigation suggested that the negative regulation of WRKY57

against B. cinerea depends on the JA signaling pathway. Chromatin immunoprecipitation

experiments revealed that WRKY57 directly binds to the promoters of JASMONATE ZIM-

DOMAIN 1 (JAZ1) and JAZ5, encoding two important repressors of the JA signaling

pathway, and activates their transcription. In vivo and in vitro experiments demonstrated

that WRKY57 interacts with nuclear-encoded SIGMA FACTOR BINDING PROTEIN1 (SIB1)

and SIB2. Further experiments display that the same domain, the VQ motif, of SIB1 and

SIB2 interact with WRKY33 and WRKY57. Moreover, transient transcriptional activity

assays confirmed that WRKY57 and WRKY33 competitively regulate JAZ1 and JAZ5, SIB1

and SIB2 further enhance these competitions of WRKY57 to WRKY33. Therefore,

coordinated regulation of Arabidopsis against B. cinerea by transcription activators and

repressors would benefit plants by allowing fine regulation of defense.

Jibril, S. M., Jakada, B. H., Kutama, A. S., & Umar, H. Y. (2016). Plant and Pathogens:

Pathogen Recognision, Invasion and Plant Defense Mechanism. International Journal of

Current Microbiology and Applied Sciences, 5(6), 247257.

https://doi.org/10.20546/ijcmas.2016.506.028

A plant pathogen is an organism or a virus that can inhabit and survive on plants and can

compromise the health of the plant causing disease symptoms. Plant pathogens may be

fungi, bacteria, viruses or nematodes, covering different levels of host specificity, some

with a broad host range, others host species specific. Fungi belong to eukaryote group of

organisms which also includes moulds, yeast and mushrooms. Most of the over 100,000

species of fungi are saprophytes. However, over 20,000 species of fungi are parasites

and cause disease in crops and plants, Fungi can cause general or localized signs and/or

symptoms. In the majority of cases, fungal infections cause general necrosis of host

tissue and often cause stunting, distortions and abnormal changes in plant tissue and

organs. Bacteria are single-celled microorganisms, generally ranging from 1-2 �m in size

that cannot be seen with the unaided eye. Plant associated bacteria may be beneficial or

detrimental. There are around 200 species of phytopathogenic bacteria and almost all of

them are parasites within the plant, on its surface, in plant debris or in the soil as

saprophytes. They include leaf spots, blights, wilts, scabs, cankers and soft rots of roots,

storage organs and fruit, and overgrowth. Viruses are infectious pathogens that are too

small to be seen with a light microscope, but despite their small size they can cause

chaos. The simplest viruses are composed of a small piece of nucleic acid surrounded by

a protein coat. All viruses are obligate parasites that depend on the cellular machinery of

their hosts to reproduce. Viruses are not active outside of their hosts, and this has led

some people to suggest that they are not alive and most viruses infect only one type of

host. Most plant viruses are actively transmitted from infected to healthy plants by a

living organism called a vector. Plant-feeding arthropods, nematodes and plant-parasitic

fungi are the major types of vector organisms for plant viruses. Nematodes are

roundworms, similar to the animal parasites encountered in livestock and pets. Soil-

dwelling nematodes are both good guys and bad guys in crop production. Plant-

pathogenic nematodes feed only on plants; in fact, they cannot sustain themselves on

anything else. When their numbers increase to high levels, they can severely injure or kill

plants, especially seedlings. In lower, more typical numbers, they can cause yield losses

without causing obvious symptoms, and they can be involved in disease interactions with

other pathogens, including viruses, fungi, and bacteria. Plant-parasitic nematodes range

from 250 um to 12 mm in length, averaging 1 mm, to about 15-35 um in width. The

ability of plants to respond to challenge by potential pathogens implies that plants

recognise these potential pathogens as ’non-self. Plants defend themselves against

pathogens by a combination of weapons termed as host resistsnce from two arsenals: (1)

structural characteristics that act as physical barriers and inhibit the pathogen from

gaining entrance and spreading through the plant and (2) biochemical reactions that take

place in the cells and tissues of the plant and produce substances that are either toxic to

the pathogen or create conditions that inhibit growth of the pathogen in the plant.

Keshavarz-Tohid, V., Taheri, P., Taghavi, S. M., & Tarighi, S. (2016). The role of nitric

oxide in basal and induced resistance in relation with hydrogen peroxide and antioxidant

enzymes. Journal of Plant Physiology, 199, 29‑38.

https://doi.org/10.1016/j.jplph.2016.05.005

Nitric oxide (NO) is one of the main signal molecules, which is involved in plant growth

and development and can change regular physiological activity in biotic and abiotic

stresses. In this study, the role of NO in induced resistance with Pseudomonas

fluorescent (CHA0) and basal resistance against Rhizoctonia solani in bean plant was

investigated. Our results revealed that P. fluorescent and R. solani can increase NO

production at 6h post inoculation (hpi). Also, using the NO donor S-nitroso-N-acetyl D-

penicillamine (SNAP) led to increase NO and bean plant resistance against R. solani.

Utilizing the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethy-limidazoline-1-oxyl-

3-oxide (cPTIO), not only decreased basal resistance but also reduced induced

resistance. In continue, the activity of antioxidant enzymes was studied in the former

treatments. SNAP, CHA0 and R. solani increased the activity of peroxidase (POX),

catalase (CAT) and ascorbate peroxidase (APX) at 6, 12 and 24h post inoculation (hpi).

In contrast, using cPTIO and R. solani simultaneously (cPTIO+R) showed reduction in

activity of POX and APX at 6 hpi. The cPTIO+R treatment increased POX, APX and CAT

activity at 12 and 24 hpi. Hydrogen peroxide (H2O2) monitoring in the leaf discs clarified

that SNAP can increase H2O2 production like CHA0 and R. solani. On the other hand,

SNAP increased the resistance level of leaf discs against R. solani. Treating the leaf discs

with cPTIO led to decrease resistance against the pathogen. These leaf discs showed

reduction in H2O2 production at 6 hpi and suddenly enhanced H2O2 generation was

observed at 24hpi. This study showed that CHA0 can increase NO level in bean plants.

NO induced H2O2 generation and regulated redox state of the host plant. This interaction

resulted in significant defense against the pathogen.

Li, L., Guo, P., Jin, H., & Li, T. (2016). Different Proteomics of Ca2+ on SA-Induced

Resistance to Botrytis Cinerea in Tomato. Horticultural Plant Journal.

https://doi.org/10.1016/j.hpj.2016.08.004

To comprehensively study the effects of Ca2+ on the SA-induced resistance Botrytis

cinerea in tomato though proteomics analysis. A proteomic approach was used to

uncover the inducible proteins of tomato in the susceptible tomato cultivars ‘L402’

against Botrytis cinerea after salicylic acid (SA) and a combination treatment of CaCl2

and SA. The results showed that the use of combination treatment of CaCl2 and SA

significantly enhanced tomato resistance against Botrytis cinerea. In total, 46

differentially expressed protein spots from 2-DE gel maps were detected, of which 41

were identified by mass spectrometry. All the identified proteins were categorized into

eight groups according to their putative functions: defense response (14.00%),

antioxidative protein (9.75%), photosynthesis (24.39%), molecular chaperone (4.88%),

energy (17.01%), metabolism (21.95%), protein synthesis (4.88%) and signal

transduction (0.2%). Of the proteins in the eight function groups, the effect of

stress/defense and reactive oxygen species on Ca2+-regulated SA-induced resistance

may be the most important one in induced resistance by RT-PCR. The expression level of

pathogenesis-related proteins (PRs) and chitinase were upregulated by a combination

treatment of CaCl2 and SA. The characterization of these proteins greatly helped to

reveal the induced proteins involved in the regulation of Ca2+ on SA-induced resistance

to Botrytis cinerea. In the combination treatment of CaCl2 and SA, the defense response

and antioxidative protein were clearly up-regulated much more than SA alone or the

control treatment by the method of proteomics and RT-PCR. The present findings suggest

that susceptible tomato cultivars treated by the combination treatment of CaCl2 and SA

might possess a more sensitive SA signaling system or effective pathway than SA

treatment alone. In addition, results indicated that SA could coordinate other cellular

activities linked with photosynthesis and metabolism to facilitate defense response and

recovery, indicating that the self-defense capability of tomato was improved by the

combination treatment of CaCl2 and SA.

Liu, S. L., Wu, J., Zhang, P., Hasi, G., Huang, Y., Lu, J., & Zhang, Y. L. (2016). Response

of phytohormones and correlation of SAR signal pathway genes to the different

resistance levels of grapevine against Plasmopara viticola infection. Plant Physiology and

Biochemistry, 107, 56‑66. https://doi.org/10.1016/j.plaphy.2016.05.020

Phytohormones play an important role in the process of disease resistance in plants.

Here, we investigated which among salicylic acid, jasmonic acid, and abscisic acid

performs a key role in plant defense after Plasmopara viticola infection in grapevine. We

used grapevines possessing different resistance levels against P. viticola infection to

study the relationship between the expression of key genes in the related resistance

signaling pathways and the level of resistance. We performed high-performance liquid

chromatography–mass spectrometry to estimate the phytohormone contents in grape

leaves at different time points after the infection. Furthermore, we performed

quantitative analyses of key genes such as EDS1, PAD4, ICS2, PAL, NPR1, TGA1, and

PR1 in the systemic acquired resistance pathway by quantitative reverse transcription-

polymerase chain reaction. The results showed an increased variation in the SA content,

which was maintained at high levels, after P. viticola infection in plant species exhibiting

stronger resistance to the pathogen; this finding highlights the importance of SA in plant

defense mechanisms. Moreover, EDS1 and PAD4 expression did not show a positive

correlation with disease resistance in grape; however, higher expression of other genes

that were analyzed was observed in highly resistant grape varieties. Our results provide

insights into the role of phytohormone regulation in the induction and maintenance of

plant defense response to pathogens.

Liu, W., & Wang, G. L. (2016). Plant innate immunity in rice: a defense against pathogen

infection. National Science Review, nww015. https://doi.org/10.1093/nsr/nww015

A large number of pathogenic microorganisms cause rice diseases that lead to enormous

yield losses worldwide. Such losses are important because rice is a staple food for more

than half of the world’s population. Over the past two decades, the extensive study of the

molecular interactions between rice and the fungal pathogen Magnaporthe oryzae and

between rice and the bacterial pathogen Xanthomonas oryzae pv. oryzae has made rice a

model for investigating plant–microbe interactions of monocotyledons. Impressive

progress has been recently achieved in understanding the molecular basis of rice

pathogen-associated molecular pattern (PAMP)-immunity and effector-triggered

immunity. Here, we briefly summarize these recent advances, emphasizing the diverse

functions of the structurally conserved fungal effectors, the regulatory mechanisms of the

immune receptor complexes, and the novel strategies for breeding disease resistance.

We also discuss future research challenges.

López Sánchez, A., H.M.Stassen, J., Furci, L., Smith, L. M., & Ton, J. (2016). The role of

DNA (de)methylation in immune responsiveness of Arabidopsis. The Plant Journal, n/a-

n/a. https://doi.org/10.1111/tpj.13252

DNA methylation is antagonistically controlled by DNA-methyltransferases and DNA-

demethylases. The level of DNA methylation controls plant gene expression on a global

level. We have examined impacts of global changes in DNA methylation on the

Arabidopsis immune system. A range of hypo-methylated mutants displayed enhanced

resistance to the biotrophic pathogen Hyaloperonospora arabidopsidis (Hpa), whereas

two hyper-methylated mutants were more susceptible to this pathogen. Subsequent

characterization of the hypo-methylated nrpe1 mutant, which is impaired in RNA-directed

DNA methylation, and the hyper-methylated ros1 mutant, which is affected in DNA

demethylation, revealed that their opposite resistance phenotypes are associated with

changes in cell wall defence and salicylic acid (SA)-dependent gene expression. Against

infection by the necrotrophic pathogen Plectosphaerella cucumerina, nrpe1 showed

enhanced susceptibility, which was associated with repressed sensitivity of jasmonic acid

(JA)-inducible gene expression. Conversely, ros1 displayed enhanced resistance to

necrotrophic pathogens, which was not associated with increased responsiveness of JA-

inducible gene expression. Although nrpe1 and ros1 were unaffected in systemic acquired

resistance to Hpa, they failed to develop transgenerational acquired resistance against

this pathogen. Global transcriptome analysis of nrpe1 and ros1 at multiple time-points

after Hpa infection revealed that 49% of the pathogenesis-related transcriptome is

influenced by NRPE1- and ROS1-controlled DNA methylation. Of the 166 defence-related

genes displaying augmented induction in nrpe1 and repressed induction in ros1, only 25

genes were associated with a nearby transposable element and NRPE1- and/or ROS1-

controlled DNA methylation. Accordingly, we propose that the majority of NRPE1- and

ROS1-dependent defence genes are regulated in trans by DNA methylation. This article is

protected by copyright.

Mhlongo, M. I., Piater, L. A., Madala, N. E., Steenkamp, P. A., & Dubery, I. A. (2016).

Phenylpropanoid Defences in Nicotiana tabacum Cells: Overlapping Metabolomes Indicate

Common Aspects to Priming Responses Induced by Lipopolysaccharides, Chitosan and

Flagellin-22. PloS One, 11(3), e0151350. https://doi.org/10.1371/journal.pone.0151350

Plants have evolved both constitutive and inducible defence strategies to cope with

different biotic stimuli and stresses. Exposure of a plant to a challenging stress can lead

to a primed state that allows it to launch a more rapid and stronger defence. Here we

applied a metabolomic approach to study and compare the responses induced in

Nicotiana tabacum cells by microbe-associated molecular pattern (MAMP) molecules,

namely lipopolysaccharides (LPS), chitosan (CHT) and flagellin-22 (FLG22). Early

response metabolites, extracted with methanol, were analysed by UHPLC-MS/MS. Using

multivariate statistical tools the metabolic profiles induced by these elicitors were

analysed. In the metabolic fingerprint of these agents a total of 19 cinnamic acid

derivatives conjugated to quinic acids (chlorogenic acids), shikimic acid, tyramine,

polyamines or glucose were found as discriminant biomarkers. In addition, treatment

with the phytohormones salicylic acid (SA), methyljasmonic acid (MJ) and abscisic acid

(ABA) resulted in differentially-induced phenylpropanoid pathway metabolites. The

results indicate that the phenylpropanoid pathway is activated by these elicitors while

hydroxycinnamic acid derivatives are commonly associated with the metabolic response

to the MAMPs, and that the activated responses are modulated by both SA and MJ, with

ABA not playing a role.

Miyashita, Y., Atsumi, G., & Nakahara, K. S. (2016). Trade-offs for viruses in overcoming

innate immunities in plants. Molecular Plant-Microbe Interactions: MPMI.

https://doi.org/10.1094/MPMI-05-16-0103-CR

Plants recognize viral infection via an immune receptor: nucleotide-binding site (NB)-

leucine-rich repeat (LRR) proteins. Another immune receptor, receptor-like

kinase/proteins, which share an LRR domain with NB-LRRs, perceive conserved molecules

of pathogens called pathogen- or microbe-associated molecular patterns, but NB-LRRs

generally perceive particular viral proteins. As viruses can evolve more rapidly than the

host immune system, how do plant immune systems, which rely on the perception of

proteins, remain effective? Viral adaptive evolution may be controlled by penalties that

result from mutations in viral proteins that are perceived by NB-LRRs. Our recent studies

in pea (Pisum sativum) suggest a penalty of increased susceptibility to another immune

system: when a viral protein mutates to evade one immune system, the virus with the

mutated protein becomes more susceptible to another. Such antagonistic pleiotropy of a

viral protein by two independent plant immune systems may have precedents. Plants

may rely on pairs of immune systems to constrain adaptive evolution by viruses and

thereby maintain durable antiviral immunity.

Naselli, M., Urbaneja, A., Siscaro, G., Jaques, J. A., Zappalà, L., Flors, V., & Pérez-Hedo,

M. (2016). Stage-Related Defense Response Induction in Tomato Plants by Nesidiocoris

tenuis. International Journal of Molecular Sciences, 17(8).

https://doi.org/10.3390/ijms17081210

The beneficial effects of direct predation by zoophytophagous biological control agents

(BCAs), such as the mirid bug Nesidiocoris tenuis, are well-known. However, the benefits

of zoophytophagous BCAs’ relation with host plants, via induction of plant defensive

responses, have not been investigated until recently. To date, only the females of certain

zoophytophagous BCAs have been demonstrated to induce defensive plant responses in

tomato plants. The aim of this work was to determine whether nymphs, adult females,

and adult males of N. tenuis are able to induce defense responses in tomato plants.

Compared to undamaged tomato plants (i.e., not exposed to the mirid), plants on which

young or mature nymphs, or adult males or females of N. tenuis fed and developed were

less attractive to the whitefly Bemisia tabaci, but were more attractive to the parasitoid

Encarsia formosa. Female-exposed plants were more repellent to B. tabaci and more

attractive to E. formosa than were male-exposed plants. When comparing young- and

mature-nymph-exposed plants, the same level of repellence was obtained for B. tabaci,

but mature-nymph-exposed plants were more attractive to E. formosa. The repellent

effect is attributed to the signaling pathway of abscisic acid, which is upregulated in N.

tenuis-exposed plants, whereas the parasitoid attraction was attributed to the activation

of the jasmonic acid signaling pathway. Our results demonstrate that all motile stages of

N. tenuis can trigger defensive responses in tomato plants, although these responses

may be slightly different depending on the stage considered.

Nyalugwe, E. P., Barbetti, M. J., Clode, P. L., & Jones, R. A. C. (2016). Systemic

Hypersensitive Resistance to Turnip mosaic virus in Brassica juncea is Associated With

Multiple Defense Responses, Especially Phloem Necrosis and Xylem Occlusion. Plant

Disease, PDIS-12-15-1459-RE. https://doi.org/10.1094/PDIS-12-15-1459-RE

Systemic hypersensitive resistance (SHR) caused by Turnip mosaic virus (TuMV) was

studied by light microscopy and histochemical analysis in stem cross sections of Brassica

juncea (Indian mustard) plants. Ten TuMV isolates were inoculated to leaves of

susceptible line JM 06006, cv. Oasis CI, which carries TuMV systemic hypersensitivity

gene TuRBJU 01, and F3 progeny plants obtained from a cross between them. Systemic

mosaic (SM) symptoms were induced by all 10 isolates in plants of JM 06006, and by

resistance-breaking isolate NSW-3 in all cv. Oasis CI and F3 plants. With the other nine

isolates, cv. Oasis CI plants developed SHR while F3 progeny plants segregated for both

phenotypes; mock-inoculated control plants never became infected. Presence of SHR did

not delay systemic invasion as this commenced within 2 hours after inoculation (hai) and

was almost complete by 72 hai regardless of whether plants subsequently developed SHR

or SM. When stem cross sections sampled 9 to 12 days after inoculation were examined

for the plant defense responses, phloem necrosis, hydrogen peroxide accumulation, and

additional lignin deposition, sections from plants with SHR demonstrated all of these

characteristics, but sections from plants with SM or mock-inoculation did not. Based on

consolidated data from all isolates except NSW-3, stems developing SHR had significantly

more occluded xylem vessels (P < 0.001) compared with stems from plants developing

SM or mock-inoculated plants. Both light microscopy and histochemical tests with

phloroglucinol-HCl and toluidine blue O indicated that the xylem occlusions could be gels.

Thus, phloem necrosis, xylem occlusion, lignification, and hydrogen peroxide

accumulation were all associated with the SHR in B. juncea plants carrying TuMV

hypersensitivity gene TuRBJU 01. In addition, virus inclusion bodies were fewer in

sections from plants with SHR. Phloem necrosis was apparently acting as the primary

cause of SHR and xylem occlusion as an important secondary cause.

Pandey, D., Rajendran, S. R. C. K., Gaur, M., Sajeesh, P. K., & Kumar, A. (2016). Plant

Defense Signaling and Responses Against Necrotrophic Fungal Pathogens. Journal of

Plant Growth Regulation, 1‑16. https://doi.org/10.1007/s00344-016-9600-7

Fungal necrotrophic pathogens cause widespread crop losses and infect a variety of

plants. The perception of these pathogens or their associated signals by specific

receptors in plants triggers the mitogen-activated protein kinase (MAPK) cascades and

activates hormone (jasmonates and ethylene)-dependent and hormone-independent

signaling, which facilitates the mounting of a defense response against the invading

necrotrophs. This response involves the activation of specific transcription factors that

result in the production of antifungal proteins (plant defensins) or accumulation of

defensive secondary metabolites (phytoalexins). The perception and communication

mechanisms triggered by pathogen-associated molecular patterns and the hormones are

coordinated by the MAPK signaling cascades which integrate various aspects of the multi-

layered plant defense response. This review focuses on compiling distinct and

overlapping roles played by various components of the plant signaling machinery in

recognizing and mounting a regulated defense response against necrotrophic fungal

pathogens.

Pellissier, L., Moreira, X., Danner, H., Serrano, M., Salamin, N., van Dam, N. M., &

Rasmann, S. (2016). The simultaneous inducibility of phytochemicals related to plant

direct and indirect defences against herbivores is stronger at low elevation. Journal of

Ecology, n/a-n/a. https://doi.org/10.1111/1365-2745.12580

1. Ecological theory indicates that warmer and more stable climates should result in

stronger biotic interactions. Therefore, plant species growing at lower elevations and

experiencing greater herbivore pressure, should invest in higher levels of defences than

those at higher elevations. Nonetheless, there are a number of studies that have found

no effect of elevational gradients on plant defensive traits. Several factors might explain

the lack of consistency for the altitude-defence relationships; including 1) the reduction

of all defensive traits into one measure of resistance; 2) not considering plant defence as

the simultaneous expression of several defensive traits; and 3) not considering the

relative influence of biotic (e.g. herbivory) and abiotic (e.g. climate and soil conditions)

factors associated with the ecological gradient. 2. Here, we present a comprehensive test

of the effects of elevation and its associated biotic and abiotic factors on the individual

and simultaneous expression of constitutive direct and indirect defences and their

inducibility (i.e. expression of defences after herbivore attack). Specifically, we estimated

climatic and soil variables and measured herbivore damage and constitutive and

jasmonic acid-induced glucosinolate levels in the leaves as a proxy for direct defences,

and volatile emission as a proxy for indirect defences in 16 Cardamine species naturally

growing along the steep elevational gradient of the Alps. 3. Within a phylogenetic

comparative framework, we found that species growing at lower elevations invested

more in the simultaneous inducibility of both direct and indirect defences, whereas

species growing at higher elevations invested more in constitutive direct defences.

Although we found strong elevation gradients in herbivory and climatic and soil variables,

these biotic and abiotic factors only partially explained elevational patterns in plant

defences. 4. Synthesis - These results highlight that the complex regulation of multiple

defence traits strongly vary across elevational gradients and build towards a better

understanding of the multiple mechanisms underlying trait evolution and species

interactions along ecological gradients. This article is protected by copyright.

Perazzolli, M., Palmieri, M. C., Matafora, V., Bachi, A., & Pertot, I. (2016).

Phosphoproteomic analysis of induced resistance reveals activation of signal transduction

processes by beneficial and pathogenic interaction in grapevine. Journal of Plant

Physiology, 195, 59–72. https://doi.org/10.1016/j.jplph.2016.03.007

Protein phosphorylation regulates several key processes of the plant immune system.

Protein kinases and phosphatases are pivotal regulators of defense mechanisms elicited

by resistance inducers. However, the phosphorylation cascades that trigger the induced

resistance mechanisms in plants have not yet been deeply investigated. The beneficial

fungus Trichoderma harzianum T39 (T39) induces resistance against grapevine downy

mildew (Plasmopara viticola), but its efficacy could be further improved by a better

understanding of the cellular regulations involved. We investigated quantitative changes

in the grapevine phosphoproteome during T39-induced resistance to get an overview of

regulatory mechanisms of downy mildew resistance. Immunodetection experiments

revealed activation of the 45 and 49 kDa kinases by T39 treatment both before and after

pathogen inoculation, and the phosphoproteomic analysis identified 103 phosphopeptides

that were significantly affected by the phosphorylation cascades during T39-induced

resistance. Peptides affected by T39 treatment showed comparable phosphorylation

levels after P. viticola inoculation, indicating activation of the microbial recognition

machinery before pathogen infection. Phosphorylation profiles of proteins related to

photosynthetic processes and protein ubiquitination indicated a partial overlap of cellular

responses in T39-treated and control plants. However, phosphorylation changes of

proteins involved in response to stimuli, signal transduction, hormone signaling, gene

expression regulation, and RNA metabolism were exclusively elicited by P. viticola

inoculation in T39-treated plants. These results highlighted the relevance of

phosphorylation changes during T39-induced resistance and identified key regulator

candidates of the grapevine defense against downy mildew.

Rai, R. (2016). Role of Secondary Metabolites in Plant Defence Mechanism. Global

Journal For Research Analysis, 5(4). Consulté à l’adresse

http://worldwidejournals.in/ojs/index.php/gjra/article/view/2574

Secondary metabolites found in plants have a role in defence against herbivores, pests

and pathogens. In thisreviewwe have discussedrole of metabolites in plant defence. The

role of secondary metabolites in defence may involve deterrent and anti-feedantactivity,

toxicity or acting as precursors to physical defence systems. Role of both

cyanogenicglucosides and glucosinolates, phenolics are discussed as defensive

compounds. Biochemistry of metabolites and their formation are discussed. An enormous

variety of secondary metabolites are derived from shikimic acid or aromatic amino

acids,many of which have important roles in defence mechanisms. Several classes of

secondary’ products are induced through environmental stresses,infection, wounding or

herbivory. Role ofsalicyiates and jasmonates have been discussed as signalsand in many

other physiologicalprocesses.

Sahu, P. P., Sharma, N., Puranik, S., Chakraborty, S., & Prasad, M. (2016). Tomato 26S

Proteasome subunit RPT4a regulates ToLCNDV transcription and activates hypersensitive

response in tomato. Scientific Reports, 6, 27078. https://doi.org/10.1038/srep27078

Involvement of 26S proteasomal subunits in plant pathogen-interactions, and the roles of

each subunit in independently modulating the activity of many intra- and inter-cellular

regulators controlling physiological and defense responses of a plant were well reported.

In this regard, we aimed to functionally characterize a Solanum lycopersicum 26S

proteasomal subunit RPT4a (SlRPT4) gene, which was differentially expressed after

Tomato leaf curl New Delhi virus (ToLCNDV) infection in tolerant cultivar H-88-78-1.

Molecular analysis revealed that SlRPT4 protein has an active ATPase activity. SlRPT4

could specifically bind to the stem-loop structure of intergenic region (IR), present in

both DNA-A and DNA-B molecule of the bipartite viral genome. Lack of secondary

structure in replication-associated gene fragment prevented formation of DNA-protein

complex suggesting that binding of SlRPT4 with DNA is secondary structure specific.

Interestingly, binding of SlRPT4 to IR inhibited the function of RNA Pol-II and

subsequently reduced the bi-directional transcription of ToLCNDV genome. Virus-induced

gene silencing of SlRPT4 gene incited conversion of tolerant attributes of cultivar H-88-

78-1 into susceptibility. Furthermore, transient overexpression of SlRPT4 resulted in

activation of programmed cell death and antioxidant enzymes system. Overall, present

study highlights non-proteolytic function of SlRPT4 and their participation in defense

pathway against virus infection in tomato.

Shah, J., Giri, M. K., Chowdhury, Z., & Venables, B. J. (2016). Signaling function of

dehydroabietinal in plant defense and development. Phytochemistry Reviews, 1‑12.

https://doi.org/10.1007/s11101-016-9466-0

Plants provide the bulk of the nearly 12,000 diterpenoid natural products, which include

diterpene resin acids that have important medicinal and industrial applications. However,

the biological function of these terpenoids in plants is poorly understood. Here, we

highlight recent work that implicates a signaling function in angiosperms for some of

these diterpenoids. In particular, this review will focus on the involvement of an abietane

diterpenoid, dehydroabietinal, in the activation of systemic acquired resistance, and draw

attention to new evidence that supports a role for dehydroabietinal in the transition from

the vegetative phase of growth to reproductive development in the crucifer plant

Arabidopsis thaliana.

Sherwood, P., & Bonello, P. (2016). Testing the systemic induced resistance hypothesis

with Austrian pine and Diplodia sapinea. Physiological and Molecular Plant Pathology, 94,

118‑125. https://doi.org/10.1016/j.pmpp.2016.06.002

Systemic induction of defenses (e.g. phenolic metabolites) is considered vital in conifer

resistance to pathogens and insects, and forms the mechanistic basis of the systemic

induced resistance hypothesis (SIRH). In this study, the SIRH was tested on juvenile

Austrian pine. Main stems expressed SIR in a manner that was consistent with the SIRH,

while shoots became uniformly more susceptible to subsequent inoculations,

demonstrating clear organ specificity in the tree’s response. The majority of phenolic

metabolites were poorly correlated with phenotype. Thus, the defensive system of

Austrian pine is highly plastic and organ specific, and cannot be predicted by phenolic

profiles alone.

Shibata, Y., Ojika, M., Sugiyama, A., Yazaki, K., Jones, D. A., Kawakita, K., & Takemoto,

D. (2016). The Full-size ABCG Transporters Nb-ABCG1 and Nb-ABCG2 function in Pre-

and Post-invasion Defense against Phytophthora infestans in Nicotiana benthamiana. The

Plant Cell. https://doi.org/10.1105/tpc.15.00721

The sesquiterpenoid capsidiol is the major phytoalexin produced by Nicotiana and

Capsicum species. Capsidiol is produced in plant tissues attacked by pathogens and plays

a major role in post-invasion defense by inhibiting pathogen growth. Using virus-induced

gene silencing (VIGS)-based screening, we identified two Nicotiana benthamiana (wild

tobacco) genes encoding functionally-redundant full-size ABCG (PDR-type) transporters,

Nb-ABCG1/PDR1 and Nb-ABCG2/PDR2, which are essential for resistance to the potato

late blight pathogen Phytophthora infestans. Silencing of Nb-ABCG1/2 compromised

secretion of capsidiol, revealing Nb-ABCG1/2 as probable exporters of capsidiol.

Accumulation of plasma membrane-localized Nb-ABCG1 and Nb-ABCG2 was observed at

the site of pathogen penetration. Silencing of EAS (encoding 5-epi-aristolochene

synthase), a gene for capsidiol biosynthesis, reduced resistance to P. infestans, but

penetration by P. infestans was not affected. By contrast, Nb-ABCG1/2-silenced plants

showed reduced penetration defense, indicating that Nb-ABCG1/2 are involved in pre-

invasion defense against P. infestans. Plastidic GGPPS1 (Geranylgeranyl diphosphate

synthase) was also found to be required for pre-invasion defense, thereby suggesting

that plastid-produced diterpene(s) are the anti-microbial compounds active in pre-

invasion defense. These findings suggest that N. benthamiana ABCG1/2 are involved in

the export of both anti-microbial diterpene(s) for pre-invasion defense and capsidiol for

post-invasion defense against P. infestans.

Shimono, M., Higaki, T., Kaku, H., Shibuya, N., Hasezawa, S., & Day, B. (2016).

Quantitative Evaluation of Stomatal Cytoskeletal Patterns during the Activation of

Immune Signaling in Arabidopsis thaliana. PloS One, 11(7), e0159291.

https://doi.org/10.1371/journal.pone.0159291

Historically viewed as primarily functioning in the regulation of gas and water vapor

exchange, it is now evident that stomata serve an important role in plant immunity.

Indeed, in addition to classically defined functions related to cell architecture and

movement, the actin cytoskeleton has emerged as a central component of the plant

immune system, underpinning not only processes related to cell shape and movement,

but also receptor activation and signaling. Using high resolution quantitative imaging

techniques, the temporal and spatial changes in the actin microfilament array during

diurnal cycling of stomatal guard cells has revealed a highly orchestrated transition from

random arrays to ordered bundled filaments. While recent studies have demonstrated

that plant stomata close in response to pathogen infection, an evaluation of stimulus-

induced changes in actin cytoskeletal dynamics during immune activation in the guard

cell, as well as the relationship of these changes to the function of the actin cytoskeleton

and stomatal aperture, remains undefined. In the current study, we employed

quantitative cell imaging and hierarchical clustering analyses to define the response of

the guard cell actin cytoskeleton to pathogen infection and the elicitation of immune

signaling. Using this approach, we demonstrate that stomatal-localized actin filaments

respond rapidly, and specifically, to both bacterial phytopathogens and purified pathogen

elicitors. Notably, we demonstrate that higher order temporal and spatial changes in the

filament array show distinct patterns of organization during immune activation, and that

changes in the naïve diurnal oscillations of guard cell actin filaments are perturbed by

pathogens, and that these changes parallel pathogen-induced stomatal gating. The data

presented herein demonstrate the application of a highly tractable and quantifiable

method to assign transitions in actin filament organization to the activation of immune

signaling in plants.

Stampfl, H., Fritz, M., Santo, S. D., & Jonak, C. (2016). The GSK3/Shaggy-Like Kinase

ASKα Contributes to Pattern-Triggered Immunity. Plant Physiology, 171(2), 1366‑1377.

https://doi.org/10.1104/pp.15.01741

The first layer of immunity against pathogenic microbes relies on the detection of

conserved pathogen-associated molecular patterns (PAMPs) that are recognized by

pattern recognition receptors (PRRs) to activate pattern-triggered immunity (PTI).

Despite the increasing knowledge of early PTI signaling mediated by PRRs and their

associated proteins, many downstream signaling components remain elusive. Here, we

identify the Arabidopsis (Arabidopsis thaliana) GLYCOGEN SYNTHASE KINASE3

(GSK3)/Shaggy-like kinase ASKα as a positive regulator of plant immune signaling. The

perception of several unrelated PAMPs rapidly induced ASKα kinase activity. Loss of ASKα

attenuated, whereas its overexpression enhanced, diverse PTI responses, ultimately

affecting susceptibility to the bacterial pathogen Pseudomonas syringae. Glucose-6-

phosphate dehydrogenase (G6PD), the key enzyme of the oxidative pentose phosphate

pathway, provides reducing equivalents important for defense responses and is a direct

target of ASKα. ASKα phosphorylates cytosolic G6PD6 on an evolutionarily conserved

threonine residue, thereby stimulating its activity. Plants deficient for or overexpressing

G6PD6 showed a modified immune response, and the insensitivity of g6pd6 mutant

plants to PAMP-induced growth inhibition was complemented by a phosphomimetic but

not by a phosphonegative G6PD6 version. Overall, our data provide evidence that ASKα

and G6PD6 constitute an immune signaling module downstream of PRRs, linking protein

phosphorylation cascades to metabolic regulation.

Tran, P. T., Choi, H., Choi, D., & Kim, K. H. (2016). Virus-induced gene silencing reveals

signal transduction components required for the Pvr9-mediated hypersensitive response

in Nicotiana benthamiana. Virology, 495, 167‑172.

https://doi.org/10.1016/j.virol.2016.05.011

Resistance to pathogens mediated by plant resistance (R) proteins requires different

signaling transduction components and pathways. Our previous studies revealed that a

potyvirus resistance gene in pepper, Pvr9, confers a hypersensitive response (HR) to

pepper mottle virus in Nicotiana benthamiana. Our results show that the Pvr9-mediated

HR against pepper mottle virus infection requires HSP90, SGT1, NDR1, but not EDS1.

These results suggest that the Pvr9-mediated HR is possibly related to the SA pathway

but not the ET, JA, ROS or NO pathways.

Verma, V., Ravindran, P., & Kumar, P. P. (2016). Plant hormone-mediated regulation of

stress responses. BMC Plant Biology, 16(1), 86. https://doi.org/10.1186/s12870-016-

0771-y

BACKGROUND: Being sessile organisms, plants are often exposed to a wide array of

abiotic and biotic stresses. Abiotic stress conditions include drought, heat, cold and

salinity, whereas biotic stress arises mainly from bacteria, fungi, viruses, nematodes and

insects. To adapt to such adverse situations, plants have evolved well-developed

mechanisms that help to perceive the stress signal and enable optimal growth response.

Phytohormones play critical roles in helping the plants to adapt to adverse environmental

conditions. The elaborate hormone signaling networks and their ability to crosstalk make

them ideal candidates for mediating defense responses.RESULTS: Recent research

findings have helped to clarify the elaborate signaling networks and the sophisticated

crosstalk occurring among the different hormone signaling pathways. In this review, we

summarize the roles of the major plant hormones in regulating abiotic and biotic stress

responses with special focus on the significance of crosstalk between different hormones

in generating a sophisticated and efficient stress response. We divided the discussion into

the roles of ABA, salicylic acid, jasmonates and ethylene separately at the start of the

review. Subsequently, we have discussed the crosstalk among them, followed by

crosstalk with growth promoting hormones (gibberellins, auxins and cytokinins). These

have been illustrated with examples drawn from selected abiotic and biotic stress

responses. The discussion on seed dormancy and germination serves to illustrate the fine

balance that can be enforced by the two key hormones ABA and GA in regulating plant

responses to environmental signals.CONCLUSIONS: The intricate web of crosstalk among

the often redundant multitudes of signaling intermediates is just beginning to be

understood. Future research employing genome-scale systems biology approaches to

solve problems of such magnitude will undoubtedly lead to a better understanding of

plant development. Therefore, discovering additional crosstalk mechanisms among

various hormones in coordinating growth under stress will be an important theme in the

field of abiotic stress research. Such efforts will help to reveal important points of genetic

control that can be useful to engineer stress tolerant crops.

Vogel, C., Bodenhausen, N., Gruissem, W., & Vorholt, J. A. (2016). The Arabidopsis leaf

transcriptome reveals distinct but also overlapping responses to colonization by

phyllosphere commensals and pathogen infection with impact on plant health. New

Phytologist, n/a-n/a. https://doi.org/10.1111/nph.14036

* Plants are colonized by a variety of bacteria, most of which are not pathogenic.

Currently, the plant responses to phyllosphere commensals or to pathogen infection in

the presence of commensals are not well understood.* Here, we examined the

transcriptional response of Arabidopsis thaliana leaves to colonization by common

commensal bacteria in a gnotobiotic system using RNA sequencing and conducted plant

mutant assays.* Arabidopsis responded differently to the model bacteria Sphingomonas

melonis Fr1 (S.Fr1) and Methylobacterium extorquens PA1 (M.PA1). Whereas M.PA1 only

marginally affected the expression of plant genes (< 10), S.Fr1 colonization changed the

expression of almost 400 genes. For the latter, genes related to defense responses were

activated and partly overlapped with those elicited by the pathogen Pseudomonas

syringae DC3000 (Pst). As S.Fr1 is able to mediate plant protective activity against Pst,

we tested plant immunity mutants and found that the pattern-recognition co-receptor

mutant bak1/bkk1 showed attenuated S.Fr1-dependent plant protection.The experiments

demonstrate that the plant responds differently to members of its natural phyllosphere

microbiota. A subset of commensals trigger expression of defense-related genes and

thereby may contribute to plant health upon pathogen encounter.

Wang, Y., Zhou, L., Yu, X., Stover, E., Luo, F., & Duan, Y. (2016). Transcriptome Profiling

of Huanglongbing (HLB) Tolerant and Susceptible Citrus Plants Reveals the Role of Basal

Resistance in HLB Tolerance. Frontiers in Plant Science, 7, 933.

https://doi.org/10.3389/fpls.2016.00933

Huanglongbing (HLB) is currently the most destructive disease of citrus worldwide.

Although there is no immune cultivar, field tolerance to HLB within citrus and citrus

relatives has been observed at the USDA Picos farm at Ft. Pierce, Florida, where plants

have been exposed to a very high level of HLB pressure since 2006. In this study, we

used RNA-Seq to evaluate expression differences between two closely related cultivars

after HLB infection: HLB-tolerant « Jackson » grapefruit-like-hybrid trees and HLB

susceptible « Marsh » grapefruit trees. A total of 686 genes were differentially expressed

(DE) between the two cultivars. Among them, 247 genes were up-expressed and 439

were down-expressed in tolerant citrus trees. We also identified a total of 619 genes with

significant differential expression of alternative splicing isoforms between HLB tolerant

and HLB susceptible citrus trees. We analyzed the functional categories of DE genes

using two methods, and revealed that multiple pathways have been suppressed or

activated in the HLB tolerant citrus trees, which lead to the activation of the basal

resistance or immunity of citrus plants. We have experimentally verified the expressions

of 14 up-expressed genes and 19 down-expressed genes on HLB-tolerant « Jackson »

trees and HLB-susceptible « Marsh » trees using real time PCR. The results showed that

the expression of most genes were in agreement with the RNA-Seq results. This study

provided new insights into HLB-tolerance and useful guidance for breeding HLB-tolerant

citrus in the future.

Xing, M., Lv, H., Ma, J., Xu, D., Li, H., Yang, L., … Fang, Z. (2016). Transcriptome

Profiling of Resistance to Fusarium oxysporum f. sp. conglutinans in Cabbage (Brassica

oleracea) Roots. PloS One, 11(2), e0148048.

https://doi.org/10.1371/journal.pone.0148048

Fusarium wilt caused by Fusarium oxysporum f. sp. conglutinans (FOC) is a destructive

disease of Brassica crops, which results in severe yield losses. There is little information

available about the mechanism of disease resistance. To obtain an overview of the

transcriptome profiles in roots of R4P1, a Brassica oleracea variety that is highly resistant

to fusarium wilt, we compared the transcriptomes of samples inoculated with FOC and

samples inoculated with distilled water. RNA-seq analysis generated more than 136

million 100-bp clean reads, which were assembled into 62,506 unigenes (mean size =

741 bp). Among them, 49,959 (79.92%) genes were identified based on sequence

similarity searches, including SwissProt (29,050, 46.47%), Gene Ontology (GO) (33,767,

54.02%), Clusters of Orthologous Groups (KOG) (14,721, 23.55%) and Kyoto

Encyclopedia of Genes and Genomes Pathway database (KEGG) (12,974, 20.76%)

searches; digital gene expression analysis revealed 885 differentially expressed genes

(DEGs) between infected and control samples at 4, 12, 24 and 48 hours after inoculation.

The DEGs were assigned to 31 KEGG pathways. Early defense systems, including the

MAPK signaling pathway, calcium signaling and salicylic acid-mediated hypersensitive

response (SA-mediated HR) were activated after pathogen infection. SA-dependent

systemic acquired resistance (SAR), ethylene (ET)- and jasmonic (JA)-mediated

pathways and the lignin biosynthesis pathway play important roles in plant resistance.

We also analyzed the expression of defense-related genes, such as genes encoding

pathogenesis-related (PR) proteins, UDP-glycosyltransferase (UDPG), pleiotropic drug

resistance, ATP-binding cassette transporters (PDR-ABC transporters), myrosinase,

transcription factors and kinases, which were differentially expressed. The results of this

study may contribute to efforts to identify and clone candidate genes associated with

disease resistance and to uncover the molecular mechanism underlying FOC resistance in

cabbage.

Yeh, Y. H., Panzeri, D., Kadota, Y., Huang, Y. C., Huang, P. Y., Tao, C. N., … Zimmerli, L.

(2016). The Arabidopsis Malectin-Like/LRR-RLK IOS1 is Critical for BAK1-Dependent and

BAK1-Independent Pattern-Triggered Immunity. The Plant Cell.

https://doi.org/10.1105/tpc.16.00313

Plasma membrane-localized pattern recognition receptors (PRRs) such as FLAGELLIN

SENSING2 (FLS2), EF-TU RECEPTOR (EFR) and CHITIN ELICITOR RECEPTOR KINASE 1

(CERK1) recognize microbe-associated molecular patterns (MAMPs) to activate pattern-

triggered immunity (PTI). A reverse genetics approach on genes responsive to the

priming agent beta-aminobutyric acid (BABA) revealed IMPAIRED OOMYCETE

SUSCEPTIBILITY1 (IOS1) as a critical PTI player. Arabidopsis thaliana ios1 mutants were

hyper-susceptible to Pseudomonas syringae bacteria. Accordingly, ios1 mutants showed

defective PTI responses, notably delayed up-regulation of the PTI-marker gene FLG22-

INDUCED RECEPTOR-LIKE KINASE1 (FRK1), reduced callose deposition and mitogen-

activated protein kinase activation upon MAMP treatment. Moreover, Arabidopsis lines

over-expressing IOS1 were more resistant to bacteria and showed a primed PTI

response. In vitro pull-down, bimolecular fluorescence complementation, co-

immunoprecipitation, and mass spectrometry analyses supported the existence of

complexes between the membrane-localized IOS1 and BRASSINOSTEROID

INSENSITIVE1-ASSOCIATED KINASE1 (BAK1)-dependent PRRs FLS2 and EFR, as well as

with the BAK1-independent PRR CERK1. IOS1 also associated with BAK1 in a ligand-

independent manner, and positively regulated FLS2-BAK1 complex formation upon MAMP

treatment. In addition, IOS1 was critical for chitin-mediated PTI. Finally, ios1 mutants

were defective in BABA-induced resistance and priming. This work reveals IOS1 as a

novel regulatory protein of FLS2-, EFR- and CERK1-mediated signaling pathways that

primes PTI activation.

Yu, X. D., Liu, Z. C., Huang, S. L., Chen, Z. Q., Sun, Y. W., Duan, P. F., … Xia, L. Q.

(2016). RNAi-mediated Plant Protection against Aphids. Pest Management Science, n/a-

n/a. https://doi.org/10.1002/ps.4258

Aphids (Aphididae) are major agricultural pests that cause significant yield losses of crop

plants each year by inflicting damage both through the direct effects of feeding and by

vectoring harmful plant viruses. Expression of double-stranded RNA (dsRNA) directed

against suitable insect target genes in transgenic plants has been shown to give

protection against pests through plant-mediated RNA interference (RNAi). Thus, as a

potential alternative and effective strategy for insect pest management in agricultural

practice, plant-mediated RNAi for aphid control has been received intensive attention in

recent years. In this review, the mechanism of RNAi in insects and the so far explored

effective RNAi target genes in aphids, their potential applications in development of

transgenic plants for aphid control, and the major challenges in these aspects are

reviewed and the future perspectives of using plant-mediated RNAi for aphid control are

proposed. This review is intended to be a helpful insight into the generation of aphid-

resistant plants through plant-mediated RNAi strategy.

Amil-Ruiz, F., Garrido-Gala, J., Gadea, J., Blanco-Portales, R., Muñoz-Mérida, A., Trelles,

O., … Caballero, J. L. (2016). Partial Activation of SA- and JA-Defensive Pathways in

Strawberry upon Colletotrichum acutatum Interaction. Frontiers in Plant Science, 7,

1036. https://doi.org/10.3389/fpls.2016.01036

Understanding the nature of pathogen host interaction may help improve strawberry

(Fragaria × ananassa) cultivars. Plant resistance to pathogenic agents usually operates

through a complex network of defense mechanisms mediated by a diverse array of

signaling molecules. In strawberry, resistance to a variety of pathogens has been

reported to be mostly polygenic and quantitatively inherited, making it difficult to

associate molecular markers with disease resistance genes. Colletotrichum acutatum spp.

is a major strawberry pathogen, and completely resistant cultivars have not been

reported. Moreover, strawberry defense network components and mechanisms remain

largely unknown and poorly understood. Assessment of the strawberry response to C.

acutatum included a global transcript analysis, and acidic hormones SA and JA

measurements were analyzed after challenge with the pathogen. Induction of transcripts

corresponding to the SA and JA signaling pathways and key genes controlling major

steps within these defense pathways was detected. Accordingly, SA and JA accumulated

in strawberry after infection. Contrastingly, induction of several important SA, JA, and

oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1,

and FaGST1, was not detected, which suggests that specific branches in these defense

pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5, and FaPR10)

were activated. Our results reveal that specific aspects in SA and JA dependent signaling

pathways are activated in strawberry upon interaction with C. acutatum. Certain

described defense-associated transcripts related to these two known signaling pathways

do not increase in abundance following infection. This finding suggests new insight into a

specific putative molecular strategy for defense against this pathogen.

Ataide, L. M. S., Pappas, M. L., Schimmel, B. C. J., Lopez-Orenes, A., Alba, J. M., Duarte,

M. V. A., … Kant, M. R. (2016). Induced plant-defenses suppress herbivore reproduction

but also constrain predation of their offspring. Plant Science, 252, 300‑310.

https://doi.org/10.1016/j.plantsci.2016.08.004

Inducible anti-herbivore defenses in plants are predominantly regulated by jasmonic acid

(JA). On tomato plants, most genotypes of the herbivorous generalist spider mite

Tetranychus urticae induce JA defenses and perform poorly on it, whereas the

Solanaceae specialist Tetranychus evansi, who suppresses JA defenses, performs well on

it. We asked to which extent these spider mites and the predatory mite Phytoseiulus

longipes preying on these spider mites eggs are affected by induced JA-defenses. By

artificially inducing the JA-response of the tomato JA-biosynthesis mutant def-1 using

exogenous JA and isoleucine (Ile), we first established the relationship between

endogenous JA-Ile-levels and the reproductive performance of spider mites. For both

mite species we observed that they produced more eggs when levels of JA-Ile were low.

Subsequently, we allowed predatory mites to prey on spider mite-eggs derived from

wild-type tomato plants, def-1 and JA-Ile-treated def-1 and observed that they preferred,

and consumed more, eggs produced on tomato plants with weak JA defenses. However,

predatory mite oviposition was similar across treatments. Our results show that induced

JA-responses negatively affect spider mite performance, but positively affect the survival

of their offspring by constraining egg-predation.

Campos, M. L., Yoshida, Y., Major, I. T., de Oliveira Ferreira, D., Weraduwage, S. D.,

Froehlich, J. E., … Howe, G. A. (2016). Rewiring of jasmonate and phytochrome B

signalling uncouples plant growth-defense tradeoffs. Nature Communications, 7, 12570.

https://doi.org/10.1038/ncomms12570

Plants resist infection and herbivory with innate immune responses that are often

associated with reduced growth. Despite the importance of growth-defense tradeoffs in

shaping plant productivity in natural and agricultural ecosystems, the molecular

mechanisms that link growth and immunity are poorly understood. Here, we demonstrate

that growth-defense tradeoffs mediated by the hormone jasmonate are uncoupled in an

Arabidopsis mutant (jazQ phyB) lacking a quintet of Jasmonate ZIM-domain

transcriptional repressors and the photoreceptor phyB. Analysis of epistatic interactions

between jazQ and phyB reveal that growth inhibition associated with enhanced anti-

insect resistance is likely not caused by diversion of photoassimilates from growth to

defense but rather by a conserved transcriptional network that is hardwired to attenuate

growth upon activation of jasmonate signalling. The ability to unlock growth-defense

tradeoffs through relief of transcription repression provides an approach to assemble

functional plant traits in new and potentially useful ways.

Chae, E., Tran, D. T. N., & Weigel, D. (2016). Cooperation and Conflict in the Plant

Immune System. PLoS Pathogens, 12(3), e1005452.

https://doi.org/10.1371/journal.ppat.1005452

Plants have a sophisticated innate immune system with which they defend themselves

against a myriad of pathogens. During the past two decades, work in a range of species

has advanced our knowledge of the molecular and biochemical details of plant immunity.

Many of these studies have focused on the action of nucleotide-binding domain/leucine-

rich repeat (NB-LRR or NLR) immune receptors. NLR genes constitute the most diverse

gene family in plants, reflecting their role in perceiving a very diverse set of molecules

that are released by pathogens. There has also been progress in unraveling the forces

that drive diversification of NLR and non-NLR immune receptors in wild species. A major

recent insight from mechanistic and evolutionary studies is that there is both cooperation

and conflict in the plant immune system. Here, we propose that these two antagonistic

forces are inherently entangled, and that they are potentially fundamental to our

understanding of growth-defense trade-offs.

Chuang, H. W., Feng, J. H., & Feng, Y. L. (2016). The Role of Arabidopsis WDR protein in

plant growth and defense strategies. Plant Signaling & Behavior, 0.

https://doi.org/10.1080/15592324.2016.1217376

Evidence indicates that the mechanisms controlling photosynthesis efficiency also

regulate plant response to biotic and abiotic stress. Light-induced cell death is genetically

maintained for the control of innate immunity. In a recent study we showed that the

expression of AtWDR26 was induced by light, multiple plant hormones, and abiotic

stress; increased AtWDR26 strongly upregulated gene groups related to chloroplast

metabolism, disease resistance, and abiotic stress tolerance. Gain- and loss-of-function

analyses in transgenic plants demonstrated the involvement of AtWDR26 in signaling

pathways; these controls were osmotic as well as salt stress tolerance. More detailed

transcriptome evidence suggested that AtWDR26 was a powerful inducer of gene

expression associated with chloroplast metabolism. This included the electron transport

chain of the photosystem, carbohydrate synthesis, and enzymatic activity involved in

photorespiration. Moreover, genes in auxin synthesis (and perception) constituted a

significant portion of those that were upregulated. Gene expression involved in disease

resistance, control of cell wall flexibility, Zn uptake, and AP2/ERF transcription factors

was also be upregulated. We concluded that AtWDR26 is one component in the

regulatory network between light-regulated plant growth and the adaptation response to

disease resistance and abiotic stress. Auxin signal acts downstream for AtWDR26

regulation and the adaptation response to biotic and abiotic stress: this occurs through

modulating cell wall flexibility, Zn homeostasis, and controlling stress-related

transcription factors.

Couto, D., & Zipfel, C. (2016). Regulation of pattern recognition receptor signalling in

plants. Nature Reviews Immunology, 16(9), 537‑552.

https://doi.org/10.1038/nri.2016.77

Recognition of pathogen-derived molecules by pattern recognition receptors (PRRs) is a

common feature of both animal and plant innate immune systems. In plants, PRR

signalling is initiated at the cell surface by kinase complexes, resulting in the activation of

immune responses that ward off microorganisms. However, the activation and amplitude

of innate immune responses must be tightly controlled. In this Review, we summarize

our knowledge of the early signalling events that follow PRR activation and describe the

mechanisms that fine-tune immune signalling to maintain immune homeostasis. We also

illustrate the mechanisms used by pathogens to inhibit innate immune signalling and

discuss how the innate ability of plant cells to monitor the integrity of key immune

components can lead to autoimmune phenotypes following genetic or pathogen-induced

perturbations of these components.

Deleris, A., Halter, T., & Navarro, L. (2016). DNA Methylation and Demethylation in Plant

Immunity. Annual Review of Phytopathology, 54, 579‑603.

https://doi.org/10.1146/annurev-phyto-080615-100308

Detection of plant and animal pathogens triggers a massive transcriptional

reprogramming, which is directed by chromatin-based processes, and ultimately results

in antimicrobial immunity. Although the implication of histone modifications in

orchestrating biotic stress-induced transcriptional reprogramming has been well

characterized, very little was known, until recently, about the role of DNA methylation

and demethylation in this process. In this review, we summarize recent findings on the

dynamics and biological relevance of DNA methylation and demethylation in plant

immunity against nonviral pathogens. In particular, we report the implications of these

epigenetic regulatory processes in the transcriptional and co-transcriptional control of

immune-responsive genes and discuss their relevance in fine-tuning antimicrobial

immune responses. Finally, we discuss the possible yet elusive role of DNA methylation

and demethylation in systemic immune responses, transgenerational immune priming,

and de novo epiallelism, which could be adaptive.

Espinas, N. A., Saze, H., & Saijo, Y. (2016). Epigenetic Control of Defense Signaling and

Priming in Plants. Frontiers in Plant Science, 7, 1201.

https://doi.org/10.3389/fpls.2016.01201

Immune recognition of pathogen-associated molecular patterns or effectors leads to

defense activation at the pathogen challenged sites. This is followed by systemic defense

activation at distant non-challenged sites, termed systemic acquired resistance (SAR).

These inducible defenses are accompanied by extensive transcriptional reprogramming of

defense-related genes. SAR is associated with priming, in which a subset of these genes

is kept at a poised state to facilitate subsequent transcriptional regulation.

Transgenerational inheritance of defense-related priming in plants indicates the stability

of such primed states. Recent studies have revealed the importance and dynamic

engagement of epigenetic mechanisms, such as DNA methylation and histone

modifications that are closely linked to chromatin reconfiguration, in plant adaptation to

different biotic stresses. Herein we review current knowledge regarding the biological

significance and underlying mechanisms of epigenetic control for immune responses in

plants. We also argue for the importance of host transposable elements as critical

regulators of interactions in the evolutionary « arms race » between plants and

pathogens.

Genenncher, B., Wirthmueller, L., Roth, C., Klenke, M., Ma, L., Sharon, A., & Wiermer, M.

(2016). Nucleoporin-regulated MAP kinase signaling in immunity to a necrotrophic fungal

pathogen. Plant Physiology. https://doi.org/10.1104/pp.16.00832

Pathogen-responsive mitogen-activated protein kinase (MAPK or MPK) cascades relay

signals from activated immune receptors across the nuclear envelope to intra-nuclear

targets. However, in plants little is known about spatial control of MAPK signaling. Here,

we report that the nuclear pore complex (NPC) protein Nup88/MOS7 is essential for

immunity to the necrotrophic fungus Botrytis cinerea. The mos7-1 mutation, causing a

four amino-acid deletion, compromises Botrytis-induced activation of the key immune-

regulatory MAPKs MPK3/MPK6 and reduces MPK3 protein levels post-transcriptionally.

Furthermore, MOS7 contributes to retaining a sufficient MPK3 abundance in the nucleus

which is required for full immunity to B. cinerea. Finally, we present a structural model of

MOS7 and show that the mos7-1 mutation compromises interactions with Nup98a/b, two

phenylalanine-glycine repeat nucleoporins implicated in maintaining the selective NPC

permeability barrier. Together, our analysis uncovered MOS7 and Nup98 as novel

components of plant immunity towards a necrotrophic pathogen and provides

mechanistic insights into how these nucleoporins coordinate nucleocytoplasmic transport

to mount a robust immune response.

Gómez-Muñoz, N., Velázquez, K., Vives, M. C., Ruiz-Ruiz, S., Pina, J. A., Flores, R., …

Guerri, J. (2016). The resistance of sour orange to Citrus tristeza virus is mediated by

both the salycilic acid and the RNA silencing defense pathways. Molecular Plant

Pathology. https://doi.org/10.1111/mpp.12488

Citrus tristeza virus (CTV), induces in the field decline and death of citrus varieties

grafted on sour orange (SO) rootstock, which has forced the use of alternative decline-

tolerant rootstocks in affected countries, despite the highly desirable agronomic features

of the SO rootstock. Declining citrus plants display phloem necrosis below the bud union.

Also, sour orange is minimally susceptible to CTV compared to other citrus varieties,

suggesting partial resistance of SO to CTV. Here, by silencing different citrus genes with

a citrus leaf blotch virus-based vector, we have examined the implication of the RNA

silencing and salicylic acid (SA) defense pathways in the resistance of SO to CTV.

Silencing of genes RDR1, NPR1 or DCL2-DCL4, associated with these defense pathways,

enhanced virus spread and accumulation in SO plants in comparison with non-silenced

controls, whereas silencing genes NPR3-NPR4, associated with the hypersensitive

response, produced a slight decrease of CTV accumulation and reduced stunting of SO

grafted on CTV-infected rough lemon plants. We have additionally found that the CTV

RNA silencing suppressors p20 and p23 suppress also the SA signalling defense, with the

suppressor activity being higher in the most virulent isolates.

Gu, Y., Zebell, S. G., Liang, Z., Wang, S., Kang, B. H., & Dong, X. (2016). Nuclear Pore

Permeabilization Is a Convergent Signaling Event in Effector-Triggered Immunity. Cell.

https://doi.org/10.1016/j.cell.2016.07.042

Nuclear transport of immune receptors, signal transducers, and transcription factors is an

essential regulatory mechanism for immune activation. Whether and how this process is

regulated at the level of the nuclear pore complex (NPC) remains unclear. Here, we

report that CPR5, which plays a key inhibitory role in effector-triggered immunity (ETI)

and programmed cell death (PCD) in plants, is a novel transmembrane nucleoporin. CPR5

associates with anchors of the NPC selective barrier to constrain nuclear access of

signaling cargos and sequesters cyclin-dependent kinase inhibitors (CKIs) involved in ETI

signal transduction. Upon activation by immunoreceptors, CPR5 undergoes an oligomer

to monomer conformational switch, which coordinates CKI release for ETI signaling and

reconfigures the selective barrier to allow significant influx of nuclear signaling cargos

through the NPC. Consequently, these coordinated NPC actions result in simultaneous

activation of diverse stress-related signaling pathways and constitute an essential

regulatory mechanism specific for ETI/PCD induction.

Hind, S. R., Strickler, S. R., Boyle, P. C., Dunham, D. M., Bao, Z., O’Doherty, I. M., …

Martin, G. B. (2016). Tomato receptor FLAGELLIN-SENSING 3 binds flgII-28 and

activates the plant immune system. Nature Plants, 2, 16128.

https://doi.org/10.1038/nplants.2016.128

Plants and animals detect the presence of potential pathogens through the perception of

conserved microbial patterns by cell surface receptors. Certain solanaceous plants,

including tomato, potato and pepper, detect flgII-28, a region of bacterial flagellin that is

distinct from that perceived by the well-characterized FLAGELLIN-SENSING 2 receptor.

Here we identify and characterize the receptor responsible for this recognition in tomato,

called FLAGELLIN-SENSING 3. This receptor binds flgII-28 and enhances immune

responses leading to a reduction in bacterial colonization of leaf tissues. Further

characterization of FLS3 and its signalling pathway could provide new insights into the

plant immune system and transfer of the receptor to other crop plants offers the

potential of enhancing resistance to bacterial pathogens that have evolved to evade

FLS2-mediated immunity.

Huaping, H., Xiaohui, J., Lunying, W., & Junsheng, H. (2016). Chitin elicitor receptor

kinase 1 (CERK1) is required for the non-host defense response of Arabidopsis to

Fusarium oxysporum f. Sp. cubense. European Journal of Plant Pathology, 1‑8.

https://doi.org/10.1007/s10658-016-1026-3

Banana wilt disease is a typical vascular disease caused by the fungal pathogen Fusarium

oxysporum f. sp. cubense 4 (Foc 4). Pattern recognition receptors in the plant cell

membrane can recognize pathogen-associated molecular patterns (PAMPs) to activate

multi-layer defense responses, including defense gene expression, stomatal closure,

reactive oxygen species (ROS) burst and callose deposition, to limit pathogen growth. In

the present study, we found that chitin elicitor receptor kinase 1 (CERK1) was required

for the non-host resistance of Arabidopsis thaliana to Foc B2 (a strain of Foc 4). The

cerk1 mutant had weaker defense responses after Foc B2 treatment, including lower

expression of PAMP- and salicylic acid-responsive genes, no stomatal closure, lower ROS

level and less callose deposition, than that of the wild-type plant. Consistent with this,

the cerk1 mutant plants exhibited higher susceptibility to non-host pathogen Foc B2.

These results suggest the crucial importance of CERK1 in Foc B2-triggered non-host

resistance.

Khan, N. U., Liu, M., Yang, X., & Qiu, D. (2016). Fungal Elicitor MoHrip2 Induces Disease

Resistance in Rice Leaves, Triggering Stress-Related Pathways. PloS One, 11(6),

e0158112. https://doi.org/10.1371/journal.pone.0158112

MoHrip2 Magnaporthe oryzae hypersensitive protein 2 is an elicitor protein of rice blast

fungus M. oryzae. Rice seedlings treated with MoHrip2 have shown an induced resistance

to rice blast. To elucidate the mechanism underlying this MoHrip2 elicitation in rice, we

used differential-display 2-D gel electrophoresis and qRT-PCR to assess the differential

expression among the total proteins extracted from rice leaves at 24 h after treatment

with MoHrip2 and buffer as a control. Among ~1000 protein spots detected on each gel,

10 proteins were newly induced, 4 were up-regulated, and 3 were down-regulated in

MoHrip2-treated samples compared with the buffer control. Seventeen differentially

expressed proteins were detected using MS/MS analysis and categorized into six groups

according to their putative function: defense-related transcriptional factors, signal

transduction-related proteins, reactive oxygen species (ROS) production, programmed

cell death (PCD), defense-related proteins, and photosynthesis and energy-related

proteins. The qPCR results (relative expression level of genes) further supported the

differential expression of proteins in MoHrip2-treated rice leaves identified with 2D-gel,

suggesting that MoHrip2 triggers an early defense response in rice leaves via stress-

related pathways, and the results provide evidence for elicitor-induced resistance at the

protein level.

Ku, K. M., Becker, T. M., & Juvik, J. A. (2016). Transcriptome and Metabolome Analyses

of Glucosinolates in Two Broccoli Cultivars Following Jasmonate Treatment for the

Induction of Glucosinolate Defense to Trichoplusia ni (Hübner). International Journal of

Molecular Sciences, 17(7), 1135. https://doi.org/10.3390/ijms17071135

Lepidopteran larvae growth is influenced by host plant glucosinolate (GS) concentrations,

which are, in turn, influenced by the phytohormone jasmonate (JA). In order to elucidate

insect resistance biomarkers to lepidopteran pests, transcriptome and metabolome

analyses following JA treatments were conducted with two broccoli cultivars, Green Magic

and VI-158, which have differentially induced indole GSs, neoglucobrassicin and

glucobrassicin, respectively. To test these two inducible GSs on growth of cabbage looper

(Trichoplusia ni), eight neonate cabbage looper larvae were placed onto each of three

plants per JA treatments (0, 100, 200, 400 µM) three days after treatment. After five

days of feeding, weight of larvae and their survival rate was found to decrease with

increasing JA concentrations in both broccoli cultivars. JA-inducible GSs were measured

by high performance liquid chromatography. Neoglucobrassicin in Green Magic and

glucobrassicin in VI-158 leaves were increased in a dose-dependent manner. One or both

of these glucosinolates and/or their hydrolysis products showed significant inverse

correlations with larval weight and survival (five days after treatment) while being

positively correlated with the number of days to pupation. This implies that these two JA-

inducible glucosinolates can influence the growth and survival of cabbage looper larvae.

Transcriptome profiling supported the observed changes in glucosinolate and their

hydrolysis product concentrations following JA treatments. Several genes related to GS

metabolism differentiate the two broccoli cultivars in their pattern of transcriptional

response to JA treatments. Indicative of the corresponding change in indole GS

concentrations, transcripts of the transcription factor MYB122, core structure biosynthesis

genes (CYP79B2, UGT74B1, SUR1, SOT16, SOT17, and SOT18), an indole glucosinolate

side chain modification gene (IGMT1), and several glucosinolate hydrolysis genes (TGG1,

TGG2, and ESM1) were significantly increased in Green Magic (statistically significant in

most cases at 400 µM) while UGT74B1 and MYB122 were significantly increased in VI-

158. Therefore, these metabolite and transcript biomarker results indicate that

transcriptome profiling can identify genes associated with the formation of two different

indole GS and their hydrolysis products. Therefore, these metabolite and transcript

biomarkers could be useful in an effective marker-assisted breeding strategy for

resistance to generalist lepidopteran pests in broccoli and potentially other Brassica

vegetables.

Lee, S., Fu, F., Xu, S., Lee, S. Y., Yun, D. J., & Mengiste, T. (2016). Global regulation of

plant immunity by histone lysine methyl transferases. The Plant Cell.

https://doi.org/10.1105/tpc.16.00012

Post-translational modification of histones modulates gene expression affecting diverse

biological functions. We showed that the Arabidopsis histone methyl transferases SET

DOMAIN GROUP 8 and 25 (SDG8, SDG25) regulate pep1-, flg22-, effector-triggered

immunity and systemic acquired resistance. Genome wide basal and induced

transcriptome changes regulated by SDG8 and/or SDG25 showed that two genes of the

SDG-dependent transcriptome, CAROTENOID ISOMERASE2 (CCR2) and ECERIFERUM 3

(CER3), were also required for plant immunity, establishing mechanisms in defense

functions for SDG8 and SDG25. CCR2 catalyzes the biosynthesis of carotenoids, whereas

CER3 is involved in the biosynthesis of cuticular wax. SDG8 and SDG25 affected distinct

and overlapping global and locus-specific histone H3 lysine 4 (H3K4) and histone H3

lysine 36 (H3K36) methylations. Loss of immunity in sdg mutants was attributed to

altered global and CCR2- and CER3-specific histone lysine methylation (HLM). Loss of

immunity in sdg, ccr2 and cer3 mutants was also associated with diminished

accumulation of lipids and loss of cuticle integrity. In addition, sdg8 and sdg25 mutants

were impaired in H2B ubiquitination (H2Bubn) at CCR2, CER3 and H2Bubn regulated R-

gene, SNC1, revealing cross talk between the two types of histone modifications. In

summary, SDG8 and SDG25 contribute to plant immunity directly through HLM or

indirectly through H2Bubn and by regulating expression of plant immunity genes,

accumulation of lipids, biosynthesis of carotenoids and maintenance of cuticle integrity.

Lee, W. S., Fu, S. F., Li, Z., Murphy, A. M., Dobson, E. A., Garland, L., … Carr, J. P.

(2016). Salicylic acid treatment and expression of an RNA-dependent RNA polymerase 1

transgene inhibit lethal symptoms and meristem invasion during tobacco mosaic virus

infection in Nicotiana benthamiana. BMC Plant Biology, 16, 15.

https://doi.org/10.1186/s12870-016-0705-8

Host RNA-dependent RNA polymerases (RDRs) 1 and 6 contribute to antiviral RNA

silencing in plants. RDR6 is constitutively expressed and was previously shown to limit

invasion of Nicotiana benthamiana meristem tissue by potato virus X and thereby inhibit

disease development. RDR1 is inducible by salicylic acid (SA) and several other

phytohormones. But although it contributes to basal resistance to tobacco mosaic virus

(TMV) it is dispensable for SA-induced resistance in inoculated leaves. The laboratory

accession of N. benthamiana is a natural rdr1 mutant and highly susceptible to TMV.

However, TMV-induced symptoms are ameliorated in transgenic plants expressing

Medicago truncatula RDR1.

Li, L., Yu, Y., Zhou, Z., & Zhou, J. M. (2016). Plant pattern-recognition receptors

controlling innate immunity. Science China. Life Sciences.

https://doi.org/10.1007/s11427-016-0115-2

Li, X., Yang, D. L., Sun, L., Li, Q., Mao, B., & He, Z. (2016). The Systemic Acquired

Resistance Regulator OsNPR1 Attenuates Growth by Repressing Auxin Signaling through

Promoting IAA-Amido Synthase Expression. Plant Physiology, 172(1), 546‑558.

https://doi.org/10.1104/pp.16.00129

Systemic acquired resistance is a long-lasting and broad-spectrum disease resistance to

pathogens. Our previous study demonstrated that overexpression of NONEXPRESSOR OF

PATHOGENESIS-RELATED GENES1 (OsNPR1), a master gene for systemic acquired

resistance in rice (Oryza sativa), greatly enhanced resistance to bacterial blight caused

by Xanthomonas oryzae pv oryzae. However, the growth and development of the

OsNPR1 overexpression (OsNPR1-OX) plants were restrained, and the mechanism

remained elusive. In this study, we dissected the OsNPR1-induced growth inhibition. We

found that the OsNPR1-OX lines displayed phenotypes mimicking auxin-defective

mutants, with decreases in root system, seed number and weight, internode elongation,

and tiller number. Whole-genome expression analysis revealed that genes related to the

auxin metabolism and signaling pathway were differentially expressed between the

OsNPR1-OX and wild-type plants. Consistently, the indole-3-acetic acid (IAA) content

was decreased and the auxin distribution pattern was altered in OsNPR1-OX plants.

Importantly, we found that some GH3 family members, in particular OsGH3.8 coding

IAA-amido synthetase, were constitutively up-regulated in OsNPR1-OX plants. Decreased

OsGH3.8 expression by RNA interference could partially restore IAA level and largely

rescue the restrained growth and development phenotypes but did not affect the disease

resistance of OsNPR1-OX plants. Taken together, we revealed that OsNPR1 affects rice

growth and development by disrupting the auxin pathway at least partially through

indirectly up-regulating OsGH3.8 expression.

Li, X., Zhang, Y., Yin, L., & Lu, J. (2016). Overexpression of pathogen-induced grapevine

TIR-NB-LRR gene VaRGA1 enhances disease resistance and drought and salt tolerance in

Nicotiana benthamiana. Protoplasma. https://doi.org/10.1007/s00709-016-1005-8

The NBS-LRR proteins encoded by the majority of R genes represent important

intracellular receptors that directly or indirectly recognize pathogen effector proteins,

which subsequently activate plant defense responses. In this study, a novel Plasmopara

viticola-induced TIR-NBS-LRR gene, named VaRGA1, was cloned from leaf tissues of a

highly downy mildew-resistant Vitis amurensis « Shuanghong » grapevine. The

fluorescence signal of the VaRGA1-GFP fusion protein was clearly partitioned to the

cytoplasm and nucleus. The expression of the VaRGA1 gene was strongly induced during

early stages of infection by P. viticola, and was also significantly upregulated after

drought and salt treatments. Accordingly, grapevine leaves transiently expressing the

VaRGA1 gene manifested increased resistance to P. viticola, and the overexpression of

the VaRGA1 gene in Nicotiana benthamiana conferred enhanced resistance to

Phytophthora parasitica through the activation of salicylic acid (SA) signaling and

phenylpropanoid pathways and could also increase tolerance to drought and salt stresses

at the germination and vegetable growth stages. These findings indicate that the

grapevine VaRGA1 gene may function as the immune and non-immune receptors against

biotic and abiotic stresses and that there may be signaling overlap between biotic and

abiotic responses.

Liu, A. C., & Cheng, C. P. (2016). Pathogen-induced ERF68 regulates hypersensitive cell

death in tomato. Molecular Plant Pathology. https://doi.org/10.1111/mpp.12460

Ethylene response factors (ERFs) are a large plant-specific transcription factor family and

play diverse important roles in various plant functions. However, most tomato ERFs are

not characterized. In this study, we showed that expression of an uncharacterized

member of tomato ERF-IX subgroup, ERF68, was significantly induced by treatments of

different bacterial pathogens, ethylene (ET) and salicylic acid (SA), but only slightly

induced by bacterial mutants defective in the type III secretion system (T3SS) or non-

host pathogens. ERF68-GFP fusion protein was localized in the nucleus. Transactivation

and electrophoretic mobility shift assays (EMSA) further showed that ERF68 was a

functional transcriptional activator and bound to the GCC-box. Moreover, transient

overexpression of ERF68 led to spontaneous lesions in tomato and tobacco leaves and

enhanced expression of genes involved in ET, SA, jasmonic acid (JA) and hypersensitive

response (HR) pathways, while silencing of ERF68 increased tomato susceptibility to two

incompatible Xanthomonas spp. These results reveal the involvement of ERF68 in

effector-triggered immunity (ETI) pathway. To identify ERF68 target genes, chromatin-

immunopreciptation combined with high-throughput sequencing (ChIP-seq) was

performed. Among the confirmed target genes, a few genes involved in cell death or

disease defense were differentially regulated by ERF68. Our study demonstrates function

of ERF68 in positively regulating hypersensitive cell death and disease defense by

modulating multiple signaling pathways and provides important new information on the

complex regulatory function of ERFs. This article is protected by copyright. All rights

reserved.

Misas-Villamil, J. C., van der Hoorn, R. A. L., & Doehlemann, G. (2016). Papain-like

cysteine proteases as hubs in plant immunity. The New Phytologist.

https://doi.org/10.1111/nph.14117

Plants deploy a sophisticated immune system to cope with different microbial pathogens

and other invaders. Recent research provides an increasing body of evidence for papain-

like cysteine proteases (PLCPs) being central hubs in plant immunity. PLCPs are required

for full resistance of plants to various pathogens. At the same time, PLCPs are targeted

by secreted pathogen effectors to suppress immune responses. Consequently, they are

subject to a co-evolutionary host-pathogen arms race. When activated, PLCPs induce a

broad spectrum of defense responses including plant cell death. While the important role

of PLCPs in plant immunity has become more evident, it remains largely elusive how

these enzymes are activated and which signaling pathways are triggered to orchestrate

different downstream responses.

Naselli, M., Urbaneja, A., Siscaro, G., Jaques, J. A., Zappalà, L., Flors, V., & Pérez-Hedo,

M. (2016). Stage-Related Defense Response Induction in Tomato Plants by Nesidiocoris

tenuis. International Journal of Molecular Sciences, 17(8).

https://doi.org/10.3390/ijms17081210

The beneficial effects of direct predation by zoophytophagous biological control agents

(BCAs), such as the mirid bug Nesidiocoris tenuis, are well-known. However, the benefits

of zoophytophagous BCAs’ relation with host plants, via induction of plant defensive

responses, have not been investigated until recently. To date, only the females of certain

zoophytophagous BCAs have been demonstrated to induce defensive plant responses in

tomato plants. The aim of this work was to determine whether nymphs, adult females,

and adult males of N. tenuis are able to induce defense responses in tomato plants.

Compared to undamaged tomato plants (i.e., not exposed to the mirid), plants on which

young or mature nymphs, or adult males or females of N. tenuis fed and developed were

less attractive to the whitefly Bemisia tabaci, but were more attractive to the parasitoid

Encarsia formosa. Female-exposed plants were more repellent to B. tabaci and more

attractive to E. formosa than were male-exposed plants. When comparing young- and

mature-nymph-exposed plants, the same level of repellence was obtained for B. tabaci,

but mature-nymph-exposed plants were more attractive to E. formosa. The repellent

effect is attributed to the signaling pathway of abscisic acid, which is upregulated in N.

tenuis-exposed plants, whereas the parasitoid attraction was attributed to the activation

of the jasmonic acid signaling pathway. Our results demonstrate that all motile stages of

N. tenuis can trigger defensive responses in tomato plants, although these responses

may be slightly different depending on the stage considered.

Pastorczyk, M., & Bednarek, P. (2016). The Function of Glucosinolates and Related

Metabolites in Plant Innate Immunity. In B.-A. in B. Research (Éd.), . Academic Press.

Consulté à l’adresse

http://www.sciencedirect.com/science/article/pii/S0065229616300829

Numerous studies showed that glucosinolate metabolism products support broad

spectrum immunity in the model plant Arabidopsis thaliana and possibly other

Brassicaceae species. According to the experimental evidence, in response to pathogenic

infection, methionine-derived aliphatic glucosinolates are metabolized similarly as during

interactions with insects, and resulting products may restrict the in planta growth of at

least same nonadapted microbial pathogens. Opposite to aliphatic glucosinolates, a

specialized metabolic pathway evolved in the Brassicaceae species to metabolize the

tryptophan-derived indole glucosinolates (IGs) in response to pathogen recognition. In

addition to the activation of glucosinolate metabolism, microbial infection of Brassicaceae

species triggers the biosynthesis of indole-type phytoalexins that are interconnected with

IGs at the biosynthetic level. Unfortunately, despite years of studies the mode of action

of glucosinolate-related phytochemicals in plant immunity remains unknown. Originally,

due to their antimicrobial activity in vitro, these compounds were classified as in planta

antibiotic. However, recent experimental evidence indicate that some molecules released

during pathogen-triggered glucosinolate metabolism may activate evolutionarily

conserved immune responses, possibly through affecting glutathione redox state in the

infected cell.

Riet, K. B., Ndlovu, N., Piater, L. A., & Dubery, I. A. (2016). Simultaneous Analysis of

Defense-Related Phytohormones in Arabidopsis thaliana Responding to Fungal Infection.

Applications in Plant Sciences, 4(8), 1600013. https://doi.org/10.3732/apps.1600013

Premise of the study: Simultaneous analysis of defense-related phytohormones can

provide insights into underlying biochemical interactions. Ultra-high-performance liquid

chromatographic (UHPLC) techniques hyphenated to electrospray ionization mass

spectrometry (ESI-MS) are powerful analytical platforms, suitable for quantitative

profiling of multiple classes of metabolites. Methods: An efficient and simplified

extraction method was designed followed by reverse-phase UHPLC for separation of

seven phytohormones: salicylic acid, methyl salicylate, jasmonic acid, methyl jasmonate,

absiscic acid, indole acetic acid, and the ethylene precursor 1-aminocyclopropane-1-

carboxylic acid. A triple quadrupole multiple reaction monitoring (MRM) method was

developed for MS quantification. The methods were applied to analyze phytohormones in

Arabidopsis leaf tissue responding to biotic stresses. Results: Under the optimized

conditions, the phytohormones were separated within 15 min, with good linearities and

high sensitivity. Repeatable results were obtained, with the limits of detection and

quantification around 0.01 ng/µL (∼9 ng/g tissue). The method was validated and applied

to monitor, quantify, and compare the temporal changes of the phytohormones under

biotic stress. Discussion: Quantitative changes indicate increased production of defense

phytohormones from the various classes. The analytical method was useful and suitable

to distinguish distinctive variations in the phytohormonal profiles and balance in A.

thaliana leaves resulting from pathogen attack.

Rodriguez-Furlán, C., Salinas-Grenet, H., Sandoval, O., Recabarren, C., Arraño-Salinas,

P., Soto-Alvear, S., … Blanco-Herrera, F. (2016). The Root Hair Specific SYP123

Regulates the Localization of Cell Wall Components and Contributes to Rizhobacterial

Priming of Induced Systemic Resistance. Frontiers in Plant Science, 7, 1081.

https://doi.org/10.3389/fpls.2016.01081

Root hairs are important for nutrient and water uptake and are also critically involved the

interaction with soil inhabiting microbiota. Root hairs are tubular-shaped outgrowths that

emerge from trichoblasts. This polarized elongation is maintained and regulated by a

robust mechanism involving the endomembrane secretory and endocytic system.

Members of the syntaxin family of SNAREs (soluble N-ethylmaleimide-sensitive factor

attachment protein receptor) in plants (SYP), have been implicated in regulation of the

fusion of vesicles with the target membranes in both exocytic and endocytic pathways.

One member of this family, SYP123, is expressed specifically in the root hairs and

accumulated in the growing tip region. This study shows evidence of the SYP123 role in

polarized trafficking using knockout insertional mutant plants. We were able to observe

defects in the deposition of cell wall proline rich protein PRP3 and cell wall

polysaccharides. In a complementary strategy, similar results were obtained using a

plant expressing a dominant negative soluble version of SYP123 (SP2 fragment) lacking

the transmembrane domain. The evidence presented indicates that SYP123 is also

regulating PRP3 protein distribution by recycling by endocytosis. We also present

evidence that indicates that SYP123 is necessary for the response of roots to plant

growth promoting rhizobacterium (PGPR) in order to trigger trigger induced systemic

response (ISR). Plants with a defective SYP123 function were unable to mount a systemic

acquired resistance in response to bacterial pathogen infection and ISR upon interaction

with rhizobacteria. These results indicated that SYP123 was involved in the polarized

localization of protein and polysaccharides in growing root hairs and that this activity also

contributed to the establishment of effective plant defense responses. Root hairs

represent very plastic structures were many biotic and abiotic factors can affect the

number, anatomy and physiology of root hairs. Here, we presented evidence that

indicates that interactions with soil PGPR could be closely regulated by signaling involving

secretory and/or endocytic trafficking at the root hair tip as a quick way to response to

changing environmental conditions.

Sun, D., Zhang, X., Li, S., Jiang, C. Z., Zhang, Y., & Niu, L. (2016). LrABCF1, a GCN-type

ATP-binding cassette transporter from Lilium regale, is involved in defense responses

against viral and fungal pathogens. Planta. https://doi.org/10.1007/s00425-016-2576-5

MAIN CONCLUSION: The L. regale ATP-binding cassette transporter gene, LrABCF1

belonging to GCN subfamily, functions as a positive regulator of plant defense against

Cucumber mosaic virus, Tobacco rattle virus , and Botrytis cinerea in petunia. ATP-

binding cassette (ABC) transporters are essential for membrane translocation in diverse

biological processes, such as plant development and defense response. Here, a general

control non-derepressible (GCN)-type ABC transporter gene, designated LrABCF1, was

identified from Cucumber mosaic virus (CMV)-induced cDNA library of L. regale. LrABCF1

was up-regulated upon inoculation with CMV and Lily mottle virus (LMoV). Salicylic acid

(SA) and ethylene (ET) application and treatments with abiotic stresses such as cold,

high salinity, and wounding increased the transcript abundances of LrABCF1. Constitutive

overexpression of LrABCF1 in petunia (Petunia × hybrida) resulted in an impairment of

plant growth and development. LrABCF1 overexpression conferred reduced susceptibility

to CMV, Tobacco rattle virus (TRV), and B. cinerea infection in transgenic petunia plants,

accompanying by elevated transcripts of PhGCN2 and a few defense-related genes in SA-

signaling pathway. Our data indicate that LrABCF1 positively modulates viral and fungal

resistance.

Veselova, S. V., Burkhanova, G. F., Nuzhnaya, T. V., & Maksimov, I. V. (2016). Roles of

ethylene and cytokinins in development of defense responses in Triticum aestivum plants

infected with Septoria nodorum. Russian Journal of Plant Physiology, 63(5), 609‑619.

https://doi.org/10.1134/S1021443716050150

Effects of ethephon (2-chloroethylphosphonic acid, ET), which is a producer of ethylene,

and 1-methylcyclopropene (1-MCP), which inhibits ethylene binding with the

corresponding receptors, on defense responses caused by the causal agent of leaf blotch

(Septoria nodorum Berk.) in leaves of soft spring wheat (Triticum aestivum L.) of

cultivars contrast in the resistance to the pathogen were studied. After treatment with 1-

MCP, an induction of wheat resistance to the disease, more prominent in the susceptible

cv. Kazakhstanskaya 10 than in the resistant cv. Omskaya 35, was found. The rise in the

resistance was accompanied by rise in zeatin content in leaves, enhanced generation of

hydrogen peroxide (most likely, due to the decreased catalase activity and increased

peroxidase activity), and accumulation of transcripts of marker genes of the salicylate

signaling pathway (PR-1 and PR-2). On the contrary, in ET-treated plants, all the studied

defense responses were inhibited, and the pathogen developed more intensively. The

effect of ethylene on zeatin distribution in infected wheat leaves of the susceptible cv.

Kazakhstanskaya 10 was also found. In the 1-MCP-treated wheat leaves, cytokinins were

localized in mesophyll cells and cell walls. In the ET-treated leaves, cell walls were free of

zeatin, and the hormone concentrated in developing hyphae of the pathogen. The results

allow for the hypothesis that wheat plant resistance is controlled by antagonistic

interaction of signaling pathways of salicylic acid and ethylene with participation of

cytokinins.

Wanderley-Nogueira, A. ., Bezerra-Neto, J. P., Kido, E. A., de Araújo, F. T., Amorim, L. L.

B., Crovella, S., & Benko-Iseppon, A. M. (2016a). Plants Defense-related Cyclic Peptides:

Diversity, Structure and Applications. Current Protein & Peptide Science.

Plant growth is prone to several unfavorable factors that may compromise or impair

development and survival, including abiotic or biotic stressors. Aiming at defending

themselves, plants have developed several strategies to survive and adapt to such

adversities. Cyclotides are a family of plant-derived proteins that exhibit a diverse range

of biological activities including antimicrobial and insecticidal activities that actively

participate in plant defense processes. Three main categories of peptides have been

described: (i) Cyclotides (ii) Sunflower Trypsin Inhibitor (SFTI) and (iii) peptides MCoTI-I

and II, from Momordica cochinchinensis. They comprise proteins of approximately 30

amino acids, containing a head-to-tail cyclized backbone, with three disulfide bonds

configured in a cystine knot topology, therefore bearing greater peptide stability. Given

their features and multifunctionality, cyclotides stand out as promising sources for the

discovery of new antimicrobial agents. The present review describes cyclotide

occurrence, abundance and action in plants, also their diversity and evolution.

Considerations regarding their use in the context of biomedical and agronomical sciences

uses are also presented.

Wanderley-Nogueira, A. C., Bezerra-Neto, J. P., Kido, E. A., de Araújo, F. T., Amorim, L.

L. B., Crovella, S., & Benko-Iseppon, A. M. (2016b). Plant Elite Squad: First Defense Line

and Resistance Genes - Identification, Diversity and Functional Roles. Current Protein &

Peptide Science.

Plants exhibit sensitive mechanisms to respond to environmental stresses, presenting

some specific and non-specific reactions when attacked by pathogens, including

organisms from different classes and complexity, as viroids, viruses, bacteria, fungi and

nematodes. A crucial step to define the fate of the plant facing an invading pathogen is

the activation of a compatible Resistance (R) gene, the focus of the present review.

Different aspects regarding R-genes and their products are discussed, including pathogen

recognition mechanisms, signaling and effects on induced and constitutive defense

processes, splicing and post transcriptional mechanisms involved. There are still

countless challenges to the complete understanding of the mechanisms involving R-genes

in plants, in particular those related to the interactions with other genes of the pathogen

and of the host itself, their regulation, acting mechanisms at transcriptional and post-

transcriptional levels, as well as the influence of other types of stress over their

regulation. A magnification of knowledge is expected when considering the novel

information from the omics and systems biology.

Yun, H. S., Kang, B. G., & Kwon, C. (2016). Arabidopsis immune secretory pathways to

powdery mildew fungi. Plant Signaling & Behavior, 0.

https://doi.org/10.1080/15592324.2016.1226456

Innate immune responses in host plants begin with the recognition of pathogen-specific

nonself molecules and terminate with the secretion of immune molecules. In the

dicotyledonous model plant, Arabidopsis thaliana, two distinct secretory pathways

required for disease resistance to powdery mildew fungi have been identified so far. One

is an exocytic pathway consisting of PEN1, SNAP33 and VAMP721/722 SNARE proteins,

but the other is an efflux-mediated one composed of PEN2 atypical myrosinase and PEN3

ABC transporter. Based on the conservation of the mechanically same exocytic pathway

in the monocotyledonous plant barely, the former is regarded as an ancient secretory

pathway, whereas the latter is considered as a newly evolved one in the Brassicaceae

family including Arabidopsis. We recently identified synaptotagmin 1 as an additional

regulator of these two secretory pathways. With current results, we discuss how these

two secretory pathways contribute to Arabidopsis immunity depending on fungal

adaptedness to Arabidopsis.

Zhang, H., Hong, Y., Huang, L., Liu, S., Tian, L., Dai, Y., … Song, F. (2016). Virus-

Induced Gene Silencing-Based Functional Analyses Revealed the Involvement of Several

Putative Trehalose-6-Phosphate Synthase/Phosphatase Genes in Disease Resistance

against Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000 in Tomato.

Frontiers in Plant Science, 7, 1176. https://doi.org/10.3389/fpls.2016.01176

Trehalose and its metabolism have been demonstrated to play important roles in control

of plant growth, development, and stress responses. However, direct genetic evidence

supporting the functions of trehalose and its metabolism in defense response against

pathogens is lacking. In the present study, genome-wide characterization of putative

trehalose-related genes identified 11 SlTPSs for trehalose-6-phosphate synthase, 8

SlTPPs for trehalose-6-phosphate phosphatase and one SlTRE1 for trehalase in tomato

genome. Nine SlTPSs, 4 SlTPPs, and SlTRE1 were selected for functional analyses to

explore their involvement in tomato disease resistance. Some selected SlTPSs, SlTPPs,

and SlTRE1 responded with distinct expression induction patterns to Botrytis cinerea and

Pseudomonas syringae pv. tomato (Pst) DC3000 as well as to defense signaling

hormones (e.g., salicylic acid, jasmonic acid, and a precursor of ethylene). Virus-induced

gene silencing-mediated silencing of SlTPS3, SlTPS4, or SlTPS7 led to deregulation of

ROS accumulation and attenuated the expression of defense-related genes upon

pathogen infection and thus deteriorated the resistance against B. cinerea or Pst

DC3000. By contrast, silencing of SlTPS5 or SlTPP2 led to an increased expression of the

defense-related genes upon pathogen infection and conferred an increased resistance

against Pst DC3000. Silencing of SlTPS3, SlTPS4, SlTPS5, SlTPS7, or SlTPP2 affected

trehalose level in tomato plants with or without infection of B. cinerea or Pst DC3000.

These results demonstrate that SlTPS3, SlTPS4, SlTPS5, SlTPS7, and SlTPP2 play roles in

resistance against B. cinerea and Pst DC3000, implying the importance of trehalose and

tis metabolism in regulation of defense response against pathogens in tomato.

Helliwell, E. E., Wang, Q., & Yang, Y. (2016). Ethylene biosynthesis and signaling is

required for rice immune response and basal resistance against Magnaporthe oryzae

infection. Molecular Plant-Microbe Interactions. https://doi.org/10.1094/MPMI-06-16-

0121-R

Recent studies have suggested that ethylene enhances host resistance to fungal

pathogen Magnaporthe oryzae, the causal agent of rice blast disease. Among the six ACS

genes in rice, OsACS1 and OsACS2 are induced within 24 hours of inoculation by M.

oryzae. This induction occurs simultaneously with an increase in ethylene production

that is noticeable 12 hours post inoculation. The purpose of this study was to examine

the dynamics of ethylene production and signaling in wild type and RNAi-mediated

suppression lines deficient in ethylene production (acs2) or signaling (eil1) after

challenge with M. oryzae, as well as fungal cell wall elicitors. Ethylene-insensitive mutant

lines show an attenuated basal defense response including lower basal expression of the

genes encoding a chitin-binding receptor, pathogenesis-related (PR) proteins, and the

enzymes involved in the synthesis of diterprenoid phytoalexins, a reduction on early HR-

like cell death, and reduced incidence of callose deposition. Ethylene-deficient mutants

showed an intermediate phenotype, with a significant reduction in expression of defense-

related genes and callose deposition, but only a slight reduction in HR-like cell death. As

a result, all ethylene-insensitive mutants show increased susceptibility to M. oryzae,

whereas the ethylene-deficient lines show a slight, but less significant increase in disease

severity. These results show that ethylene signaling, and to some extent ethylene

production, are required for rice basal resistance against the blast fungus, Magnaporthe

oryzae.

Kissoudis, C., Sunarti, S., van de Wiel, C., Visser, R. G. F., Linden, C. G., & Bai, Y.

(2016). Responses to combined abiotic and biotic stress in tomato are governed by

stress intensity and resistance mechanism. Journal of Experimental Botany, 67(17), 5119

‑5132. https://doi.org/10.1093/jxb/erw285

Stress conditions in agricultural ecosystems can occur at variable intensities. Different

resistance mechanisms against abiotic stress and pathogens are deployed by plants.

Thus, it is important to examine plant responses to stress combinations under different

scenarios. Here, we evaluated the effect of different levels of salt stress ranging from

mild to severe (50, 100, and 150mM NaCl) on powdery mildew resistance and overall

performance of tomato introgression lines with contrasting levels of partial resistance, as

well as near-isogenic lines (NILs) carrying the resistance gene Ol-1 (associated with a

slow hypersensitivity response; HR), ol-2 (an mlo mutant associated with papilla

formation), and Ol-4 (an R gene associated with a fast HR). Powdery mildew resistance

was affected by salt stress in a genotype- and stress intensity-dependent manner. In

susceptible and partial resistant lines, increased susceptibility was observed under mild

salt stress (50mM) which was accompanied by accelerated cell death-like senescence. In

contrast, severe salt stress (150mM) reduced disease symptoms. Na+ and Cl−

accumulation in the leaves was linearly related to the decreased pathogen symptoms

under severe stress. In contrast, complete resistance mediated by ol-2 and Ol-4 was

unaffected under all treatment combinations, and was associated with a decreased

growth penalty. Increased susceptibility and senescence under combined stress in NIL-

Ol-1 was associated with the induction of ethylene and jasmonic acid pathway genes and

the cell wall invertase gene LIN6. These results highlight the significance of stress

severity and resistance type on the plant’s performance under the combination of abiotic

and biotic stress.

Lim, G. H., Kachroo, A., & Kachroo, P. (2016). Role of plasmodesmata and

plasmodesmata localizing proteins in systemic immunity. Plant Signaling & Behavior, 0.

https://doi.org/10.1080/15592324.2016.1219829

Systemic acquired resistance (SAR) is a highly desirable form of resistance that protects

against a broad-spectrum of pathogens. SAR involves the generation of a mobile signal

at the site of primary infection, which arms distal portions of a plant against subsequent

secondary infections. A number of diverse chemical signals contributing to SAR have

been isolated and characterized. Among these, salicylic acid (SA) functions in parallel to

azelaic acid (AzA) and glycerol-3-phosphate (G3P), and both AzA and G3P function

downstream of the free radicals nitric oxide and reactive oxygen species. We now show

that phloem loading of AzA and G3P occurs via the symplast, whereas that of SA occurs

via the apoplast. The symplastic transport of AzA and G3P is regulated by

plasmodesmata localizing protein (PDLP) 5, which together with PDLP1 also plays a

signaling role in SAR. Together, these results reveal the transport routes of SAR

associated chemical signals, and the regulatory role of PDLPs in SAR.

Liñeiro, E., Chiva, C., Cantoral, J. M., Sabidó, E., & Fernández-Acero, F. J. (2016).

Modifications of fungal membrane proteins profile under pathogenicity induction: a

proteomic analysis of Botrytis cinerea membranome. Proteomics.

https://doi.org/10.1002/pmic.201500496

Botrytis cinerea is a model fungus for the study of phytopathogenicity that exhibits a

wide arsenal of tools to infect plant tissues. Most of these factors are related to signal

transduction cascades, in which membrane proteins play a key role as a bridge between

environment and intracellular molecular processes. This work describes the first

description of the membranome of Botrytis under different pathogenicity conditions

induced by different plant-based elicitors: Glucose and Tomato Cell Wall. A discovery

proteomics analysis of membrane proteins was carried out by mass spectrometry. A total

of 2,794 proteins were successfully identified, 46% of them were classified as membrane

proteins based on the presence of transmembrane regions and lipidation. Further

analyses showed significant differences in the membranome composition depending on

the available carbon source: 804 proteins were exclusively identified when the fungus

was cultured with glucose as sole carbon source, and 251 proteins were exclusively

identified with TCW. Besides, among the 1737 common proteins, a subset of 898 proteins

presented clear differences in their abundance. GO enrichment and clustering interaction

analysis revealed changes in the composition of membranome with increase of signalling

function in glucose conditions and carbohydrate degradation process in TCW conditions.

This article is protected by copyright. All rights reserved.

Marzec, M. (2016). Strigolactones as Part of the Plant Defence System. Trends in Plant

Science. https://doi.org/10.1016/j.tplants.2016.08.010

Strigolactones (SLs) are plant hormones, described as regulators of plant growth and

development. Recently, it was proposed that these hormones might also be involved in

the biotic stress response. However, SLs do not have a universal role in plant protection,

instead only playing a part in resistance to specific pathogens.

Mbengue, M., Bourdais, G., Gervasi, F., Beck, M., Zhou, J., Spallek, T., … Robatzek, S.

(2016). Clathrin-dependent endocytosis is required for immunity mediated by pattern

recognition receptor kinases. Proceedings of the National Academy of Sciences of the

United States of America. https://doi.org/10.1073/pnas.1606004113

Sensing of potential pathogenic bacteria is of critical importance for immunity. In plants,

this involves plasma membrane-resident pattern recognition receptors, one of which is

the FLAGELLIN SENSING 2 (FLS2) receptor kinase. Ligand-activated FLS2 receptors are

internalized into endosomes. However, the extent to which these spatiotemporal

dynamics are generally present among pattern recognition receptors (PRRs) and their

regulation remain elusive. Using live-cell imaging, we show that at least three other

receptor kinases associated with plant immunity, PEP RECEPTOR 1/2 (PEPR1/2) and EF-

TU RECEPTOR (EFR), internalize in a ligand-specific manner. In all cases, endocytosis

requires the coreceptor BRI1-ASSOCIATED KINASE 1 (BAK1), and thus depends on

receptor activation status. We also show the internalization of liganded FLS2, suggesting

the transport of signaling competent receptors. Trafficking of activated PRRs requires

clathrin and converges onto the same endosomal vesicles that are also shared with the

hormone receptor BRASSINOSTERIOD INSENSITIVE 1 (BRI1). Importantly, clathrin-

dependent endocytosis participates in plant defense against bacterial infection involving

FLS2-mediated stomatal closure and callose deposition, but is uncoupled from activation

of the flagellin-induced oxidative burst and MAP kinase signaling. In conclusion, immunity

mediated by pattern recognition receptors depends on clathrin, a critical component for

the endocytosis of signaling competent receptors into a common endosomal pathway.

Mur, L. A., Simpson, C., Kumari, A., Gupta, A. K., & Gupta, K. J. (2016). Moving nitrogen

to the centre of plant defence against pathogens. Annals of Botany.

https://doi.org/10.1093/aob/mcw179

BACKGROUND: Plants require nitrogen (N) for growth, development and defence against

abiotic and biotic stresses. The extensive use of artificial N fertilizers has played an

important role in the Green Revolution. N assimilation can involve a reductase series ([Formula: see text] → [Formula: see text] → [Formula: see text]) followed by

transamination to form amino acids. Given its widespread use, the agricultural impact of

N nutrition on disease development has been extensively examined.SCOPE: When a

pathogen first comes into contact with a host, it is usually nutrient starved such that

rapid assimilation of host nutrients is essential for successful pathogenesis. Equally, the

host may reallocate its nutrients to defence responses or away from the site of attempted

infection. Exogenous application of N fertilizer can, therefore, shift the balance in favour

of the host or pathogen. In line with this, increasing N has been reported either to

increase or to decrease plant resistance to pathogens, which reflects differences in the

infection strategies of discrete pathogens. Beyond considering only N content, the use of

[Formula: see text] or [Formula: see text] fertilizers affects the outcome of plant-

pathogen interactions. [Formula: see text] feeding augments hypersensitive response-

(HR) mediated resistance, while ammonium nutrition can compromise defence.

Metabolically, [Formula: see text] enhances production of polyamines such as spermine

and spermidine, which are established defence signals, with [Formula: see text] nutrition

leading to increased γ-aminobutyric acid (GABA) levels which may be a nutrient source

for the pathogen. Within the defensive N economy, the roles of nitric oxide must also be

considered. This is mostly generated from [Formula: see text] by nitrate reductase and is

elicited by both pathogen-associated microbial patterns and gene-for-gene-mediated

defences. Nitric oxide (NO) production and associated defences are therefore [Formula:

see text] dependent and are compromised by [Formula: see text] CONCLUSION: This

review demonstrates how N content and form plays an essential role in defensive primary

and secondary metabolism and NO-mediated events.

Nie, S., & Xu, H. (2016). Riboflavin-Induced Disease Resistance Requires the Mitogen-

Activated Protein Kinases 3 and 6 in Arabidopsis thaliana. PloS One, 11(4), e0153175.

https://doi.org/10.1371/journal.pone.0153175

As a resistance elicitor, riboflavin (vitamin B2) protects plants against a wide range of

pathogens. At molecular biological levels, it is important to elucidate the signaling

pathways underlying the disease resistance induced by riboflavin. Here, riboflavin was

tested to induce resistance against virulent Pseudomonas syringae pv. Tomato DC3000

(Pst DC3000) in Arabidopsis. Results showed that riboflavin induced disease resistance

based on MAPK-dependent priming for the expression of PR1 gene. Riboflavin induced

transient expression of PR1 gene. However, following Pst DC3000 inoculation, riboflavin

potentiated stronger PR1 gene transcription. Further was suggested that the transcript

levels of mitogen-activated protein kinases, MPK3 and MPK6, were primed under

riboflavin. Upon infection by Pst DC3000, these two enzymes were more strongly

activated. The elevated activation of both MPK3 and MPK6 was responsible for enhanced

defense gene expression and resistance after riboflavin treatment. Moreover, riboflavin

significantly reduced the transcript levels of MPK3 and MPK6 by application of AsA and

BAPTA, an H2O2 scavenger and a calcium (Ca2+) scavenger, respectively. In conclusion,

MPK3 and MPK6 were responsible for riboflavin-induced resistance, and played an

important role in H2O2- and Ca2+-related signaling pathways, and this study could

provide a new insight into the mechanistic study of riboflavin-induced defense responses.

Pétriacq, P., Ton, J., Patrit, O., Tcherkez, G. G. B., & van de Gakiere, B. (2016). NAD acts

as an integral regulator of multiple defense layers. Plant Physiology.

https://doi.org/10.1104/pp.16.00780

Pyridine nucleotides, such as nicotinamide adenine dinucleotide (NAD), are crucial redox

carriers and have emerged as important signaling molecules in stress responses.

Previously, we have demonstrated in Arabidopsis thaliana (Arabidopsis) that the inducible

NAD-overproducing nadC lines are more resistant to an avirulent strain of Pseudomonas

syringae pv. tomato (Pst-AvrRpm1), which was associated with salicylic acid-dependent

defense. Here, we have further characterized the NAD-dependent immune response in

Arabidopsis. Quinolinate-induced stimulation of intracellular NAD in transgenic nadC

plants enhanced resistance against a diverse range of (a)virulent pathogens, including

Pst-AvrRpt2, Dickeya dadantii and Botrytis cinerea. Characterization of the redox status

demonstrated that elevated NAD levels induce reactive oxygen species (ROS) production

and expression of redox marker genes of the cytosol and mitochondrion. Using

pharmacological and reverse genetics approaches, we show that NAD-induced ROS

production functions independently of NADPH oxidase activity and light metabolism but

depends on mitochondrial respiration which was increased at higher NAD. We further

demonstrate that NAD primes pathogen-induced callose deposition and cell death. Mass

spectrometry analysis reveals that NAD simultaneously induces different defense

hormones and that the NAD-induced metabolic profiles are similar to that of defense-

expressing plants after treatment with pathogen-associated molecular patterns (PAMPs).

We thus conclude that NAD triggers metabolic profiles rather similar to that of PAMPs and

discuss how signaling crosstalk between defense hormones, ROS and NAD explains the

observed resistance to pathogens.

Riet, K. B., Ndlovu, N., Piater, L. A., & Dubery, I. A. (2016). Simultaneous Analysis of

Defense-Related Phytohormones in Arabidopsis thaliana Responding to Fungal Infection.

Applications in Plant Sciences, 4(8), 1600013. https://doi.org/10.3732/apps.1600013

Premise of the study: Simultaneous analysis of defense-related phytohormones can

provide insights into underlying biochemical interactions. Ultra-high-performance liquid

chromatographic (UHPLC) techniques hyphenated to electrospray ionization mass

spectrometry (ESI-MS) are powerful analytical platforms, suitable for quantitative

profiling of multiple classes of metabolites. Methods: An efficient and simplified

extraction method was designed followed by reverse-phase UHPLC for separation of

seven phytohormones: salicylic acid, methyl salicylate, jasmonic acid, methyl jasmonate,

absiscic acid, indole acetic acid, and the ethylene precursor 1-aminocyclopropane-1-

carboxylic acid. A triple quadrupole multiple reaction monitoring (MRM) method was

developed for MS quantification. The methods were applied to analyze phytohormones in

Arabidopsis leaf tissue responding to biotic stresses. Results: Under the optimized

conditions, the phytohormones were separated within 15 min, with good linearities and

high sensitivity. Repeatable results were obtained, with the limits of detection and

quantification around 0.01 ng/µL (∼9 ng/g tissue). The method was validated and applied

to monitor, quantify, and compare the temporal changes of the phytohormones under

biotic stress. Discussion: Quantitative changes indicate increased production of defense

phytohormones from the various classes. The analytical method was useful and suitable

to distinguish distinctive variations in the phytohormonal profiles and balance in A.

thaliana leaves resulting from pathogen attack.

Roeschlin, R. A., Favaro, M. A., Chiesa, M. A., Alemano, S., Vojnov, A. A., Castagnaro, A.

P., … Marano, M. R. (2016). Resistance to citrus canker induced by a variant of

Xanthomonas citri ssp. citri is associated with a hypersensitive cell death response

involving autophagy-associated vacuolar processes. Molecular Plant Pathology, n/a-n/a.

https://doi.org/10.1111/mpp.12489

Xanthomonas citri ssp. citri (X. citri) is the causal agent of Asiatic citrus canker, a disease

that seriously affects most commercially important Citrus species worldwide. We have

previously identified a natural variant, X. citri AT, that triggers a host-specific defense

response in Citrus limon. However, the mechanisms involved in this canker disease

resistance are unknown. In this work, the defense response induced by X. citri AT was

assessed by transcriptomic, physiological and ultrastructural analyses and the effects on

bacterial biofilm formation were monitored in parallel. We show that X. citri AT triggers a

hypersensitive response associated with the interference on biofilm development and

arrest of bacterial growth in C. limon. This plant response involves an extensive

transcriptional reprogramming setting in motion cell wall reinforcement, oxidative burst

and accumulation of salicylic acid (SA) and phenolic compounds. Ultrastructural analyses

revealed subcellular changes involving the activation of autophagy-associated vacuolar

processes. Our findings show the activation of SA-dependent defense in response to X.

citri AT and suggest a coordinated regulation between SA and flavonoids pathways, which

is associated with autophagy mechanisms that control pathogen invasion in C. limon.

Furthermore, this defense response protects C. limon plants from disease upon

subsequent challenges by pathogenic X. citri. This knowledge will allow to rationally

exploit the plant immune system as a biotechnological approach to manage the disease.

This article is protected by copyright. All rights reserved.

Rovenich, H., Zuccaro, A., & Thomma, B. P. H. J. (2016). Convergent evolution of

filamentous microbes towards evasion of glycan-triggered immunity. New Phytologist.

https://doi.org/10.1111/nph.14064

All filamentous microbes produce and release a wide range of glycans, which are

essential determinants of microbe–microbe and microbe–host interactions. Major cell wall

constituents, such as chitin and β-glucans, are elicitors of host immune responses. The

widespread capacity for glycan perception in plants has driven the evolution of various

strategies that help filamentous microbes to evade detection. Common strategies include

structural and chemical modifications of cell wall components as well as the secretion of

effector proteins that suppress chitin- and β-glucan-triggered immune responses. Thus,

the necessity to avoid glycan-triggered immunity represents a driving force in the

convergent evolution of filamentous microbes towards its suppression.

Sandor, R., Der, C., Grosjean, K., Anca, I., Noirot, E., Leborgne-Castel, N., … Gerbeau-

Pissot, P. (2016). Plasma membrane order and fluidity are diversely triggered by elicitors

of plant defence. Journal of Experimental Botany, erw284.

https://doi.org/10.1093/jxb/erw284

Although plants are exposed to a great number of pathogens, they usually defend

themselves by triggering mechanisms able to limit disease development. Alongside

signalling events common to most such incompatible interactions, modifications of

plasma membrane (PM) physical properties could be new players in the cell transduction

cascade. Different pairs of elicitors (cryptogein, oligogalacturonides, and flagellin) and

plant cells (tobacco and Arabidopsis) were used to address the issue of possible

modifications of plant PM biophysical properties induced by elicitors and their links to

other events of the defence signalling cascade. We observed an increase of PM order

whatever the elicitor/plant cell pair used, provided that a signalling cascade was induced.

Such membrane modification is dependent on the NADPH oxidase-mediated reactive

oxygen species production. Moreover, cryptogein, which is the sole elicitor able to trap

sterols, is also the only one able to trigger an increase in PM fluidity. The use of

cryptogein variants with altered sterol-binding properties confirms the strong correlation

between sterol removal from the PM and PM fluidity enhancement. These results propose

PM dynamics as a player in early signalling processes triggered by elicitors of plant

defence.

Sharifi, R., & Ryu, C. M. (2016). Making healthier or killing enemies? Bacterial volatile-

elicited plant immunity plays major role upon protection of Arabidopsis than the direct

pathogen inhibition. Communicative & Integrative Biology, 9(4), e1197445.

https://doi.org/10.1080/19420889.2016.1197445

Bacterial volatiles protect plants either by directly inhibiting a pathogenic fungus or by

improving the defense capabilities of plants. The effect of bacterial volatiles on fungal

growth was dose-dependent. A low dosage did not have a noticeable effect on Botrytis

cinerea growth and development, but was sufficient to elicit induced resistance in

Arabidopsis thaliana. Bacterial volatiles displayed negative effects on biofilm formation on

a polystyrene surface and in in planta leaf colonization of B. cinerea. However, bacterial

volatile-mediated induced resistance was the major mechanism mediating protection of

plants from B. cinerea. It was responsible for more than 90% of plant protection in

comparison with direct fungal inhibition. Our results broaden our knowledge of the role of

bacterial volatiles in plant protection.

Tian, S., Wang, X., Li, P., Wang, H., Ji, H., Xie, J., … Dong, H. (2016). Plant Aquaporin

AtPIP1;4 Links Apoplastic H2O2 Induction to Disease Immunity Pathways. Plant

Physiology. https://doi.org/10.1104/pp.15.01237

H2O2 is a stable component of reactive oxygen species and its production in plants

represents the successful recognition of pathogen infection and pathogen-associated

molecular patterns (PAMPs). This production of H2O2 is typically apoplastic but is

subsequently associated with intracellular immunity pathways that regulate disease

resistance, such as systemic acquired resistance (SAR) and PAMP-triggered immunity

(PTI). Here, we elucidate that an Arabidopsis thaliana aquaporin, i.e., plasma membrane

intrinsic protein AtPIP1;4, acts to close the cytological distance between H2O2 production

and functional performance. Expression of the AtPIP1;4 gene in plant leaves is inducible

by a bacterial pathogen and the expression accompanies H2O2 accumulation in the

cytoplasm. Under de novo expression conditions, AtPIP1;4 is able to mediate the

translocation of externally applied H2O2 into the cytoplasm of yeast cells. In plant cells

treated with H2O2, AtPIP1;4 functions as an effective facilitator of H2O2 transport across

plasma membranes and mediates the translocation of externally applied H2O2 from the

apoplast to the cytoplasm. The H2O2-transport role of AtPIP1;4 is essentially required for

cytoplasmic import of apoplastic H2O2 induced by the bacterial pathogen and two typical

PAMPs in the absence of induced production of intracellular H2O2. As a consequence,

cytoplasmic H2O2 quantities substantially increase while SAR and PTI are activated to

repress the bacterial pathogenicity. By contrast, loss-of-function mutation at the

AtPIP1;4 gene locus not only nullifies the cytoplasmic import of pathogen- and PAMP-

induced apoplastic H2O2 but also cancels the subsequent immune responses, suggesting

a pivotal role of AtPIP1;4 in apo-cytoplastic signal transduction in immunity pathways.

Üstün, S., Sheikh, A., Gimenez-Ibanez, S., Jones, A. M. E., Ntoukakis, V., & Börnke, F.

(2016). The proteasome acts as a hub for plant immunity and is targeted by

Pseudomonas type-III effectors. Plant Physiology. https://doi.org/10.1104/pp.16.00808

Recent evidence suggests that the ubiquitin-proteasome system (UPS) is involved in

several aspects of plant immunity and a range of plant pathogens subvert the UPS to

enhance their virulence. Here we show that proteasome activity is strongly induced

during basal defense in Arabidopsis. Mutant lines of the proteasome subunits RPT2a and

RPN12a support increased bacterial growth of virulent Pseudomonas syringae pv. tomato

DC3000 (Pst) and Pseudomonas syringae pv. maculicola ES4326. Both proteasome

subunits are required for Pathogen-associated molecular patterns (PAMP)-triggered

immunity (PTI) responses. Analysis of bacterial growth after a secondary infection of

systemic leaves revealed that the establishment of systemic-acquired resistance (SAR) is

impaired in proteasome mutants, suggesting that the proteasome also plays an

important role in defense priming and SAR. In addition, we show that Pst inhibits

proteasome activity in a type-III secretion dependent manner. A screen for type-III

effector proteins from Pst for their ability to interfere with proteasome activity revealed

HopM1, HopAO1, HopA1 and HopG1 as putative proteasome inhibitors. Biochemical

characterization of HopM1 by mass-spectrometry indicates that HopM1 interacts with

several E3 ubiquitin ligases and proteasome subunits. This supports the hypothesis that

HopM1 associates with the proteasome leading to its inhibition. Thus, the proteasome is

an essential component of PTI and SAR, which is targeted by multiple bacterial effectors.

Van Aubel, G., Cambier, P., Dieu, M., & van Cutsem, P. (2016). Plant immunity induced

by COS-OGA elicitor is a cumulative process that involves salicylic acid. Plant Science,

247, 60–70. https://doi.org/10.1016/j.plantsci.2016.03.005

Plant innate immunity offers considerable opportunities for plant protection but beside

flagellin and chitin, not many molecules and their receptors have been extensively

characterized and very few have successfully reached the field. COS-OGA, an elicitor that

combines cationic chitosan oligomers (COS) with anionic pectin oligomers (OGA),

efficiently protected tomato (Solanum lycopersicum) grown in greenhouse against

powdery mildew (Leveillula taurica). Leaf proteomic analysis of plants sprayed with COS-

OGA showed accumulation of Pathogenesis-Related proteins (PR), especially subtilisin-

like proteases. qRT-PCR confirmed upregulation of PR-proteins and salicylic acid (SA)-

related genes while expression of jasmonic acid/ethylene-associated genes was not

modified. SA concentration and class III peroxidase activity were increased in leaves and

appeared to be a cumulative process dependent on the number of sprayings with the

elicitor. These results suggest a systemic acquired resistance (SAR) mechanism of action

of the COS-OGA elicitor and highlight the importance of repeated applications to ensure

efficient protection against disease.

Wang, J., Wang, Y., Liu, X., Xu, Y., & Ma, Q. (2016). Microtubule Polymerization

Functions in Hypersensitive Response and Accumulation of H2O2 in Wheat Induced by

the Stripe Rust. BioMed Research International, 2016, 7830768.

https://doi.org/10.1155/2016/7830768

The plant cytoskeleton, including microtubules and microfilaments, is one of the

important factors in determining the polarity of cell division and growth, as well as the

interaction of plants with invading pathogens. In defense responses of wheat against the

stripe rust (Puccinia striiformis f. sp. tritici) infection, hypersensitive response is the most

crucial event to prevent the spread of pathogens. In order to reveal the effect of

microtubules on the hypersensitive cell death and H2O2 accumulation in the interaction

of wheat (Triticum aestivum) cv. Suwon 11 with an incompatible race, CYR23, wheat

leaves were treated with microtubule inhibitor, oryzalin, before inoculation. The results

showed that the frequency of infection sites with hypersensitive response occurrence was

significantly reduced, and hypersensitive cell death in wheat leaves was suppressed

compared to the control. In addition, the frequency and the incidence of infected cells

with H2O2 accumulation were also reduced after the treatment with oryzalin. Those

results indicated that microtubules are related to hypersensitive response and H2O2

accumulation in wheat induced by the stripe rust, and depolymerization of microtubules

reduces the resistance of plants to pathogen infection in incompatible interaction,

suggesting that microtubules play a potential role in the expression of resistance of

wheat against the stripe rust fungus.

Wang, X., Gao, Y., Yan, Q., & Chen, W. (2016). Salicylic acid promotes autophagy via

NPR3 and NPR4 in Arabidopsis senescence and innate immune response. Acta

Physiologiae Plantarum, 38(10), 241. https://doi.org/10.1007/s11738-016-2257-9

In Arabidopsis thaliana, the non-expresser pathogenesis-related (NPR) multigene family

members NPR1, NPR3, and NPR4 are necessary for salicylic acid (SA) perception. NPR3

and NPR4 are the CUL3 E3-ligase substrate adaptors allowing for the ubiquitination and

turnover of NPR1 by the 26s proteasome. Concurrently, roots treated with the SA agonist

benzothiadiazole accumulate autophagic bodies via NPR1-dependent signal pathway.

However, the mechanisms by which NPR3 and NPR4 regulate autophagy remain unclear.

In the present study, using single, double, and triple npr1-, npr3-, and npr4-null mutants

and wild-type plants, the following results were obtained: (1) leaf senescence progressed

faster in npr3/npr4 mutants than in wild type, suggesting that NPR3 and NPR4 negatively

regulated leaf senescence. Moreover, npr3/npr4 promoted the expression of

pathogenesis-related 1 (PR1) gene and enhanced resistance in response to avirulent

pathogen infections suppressing cell death. Still, all mutants had similar SA levels,

suggesting that NPR3 and NPR4 positive regulation of cell death and disease resistance

was not associated with SA levels; (2) the number of autophagosomes, ATG7, and

ATG8a-phosphatidylethanolamine and the concentration of free green-fluorescence

protein were lower in npr3/npr4 mutants than in wild-type plants, indicating that NPR3

and NPR4 affected the two ubiquitination-like conjugation systems during the

autophagosome formation and degradation of autophagic bodies.

Žárský, V. (2016). Clathrin in plant defense signaling and execution. Proceedings of the

National Academy of Sciences of the United States of America.

https://doi.org/10.1073/pnas.1612925113

Plant cells are equipped with a collection of membrane surface molecular « antennas »

specifically sensitive to different signals. They are mostly represented by hundreds of

receptor-like kinases (RKs): about 600 encoded in the Arabidopsis genome (1), which

allow plants to react swiftly to signals related to the progress of their own ontogeny

(intercellular communication) and also to environmental changes, including stress

situations or pathogen attack. Such surface alertness is especially important for sessile

organisms bound to be born and die at the same single spot. Not surprisingly, study of

plant RK regulation is among the most important current fields of plant research. RKs

involved in pathogen presence recognition via specific binding of pathogen activity-

related molecular species—pattern-recognition receptor kinases (PRKs)—are also studied

for practical reasons of plant protection (for a recent overview, see refs. 2⇓–4). RKs, as

most other components of the plasmalemma (PM), are not static. Even without

activation, RKs undergo constitutive recycling to and from the PM by insertion

(exocytosis) and removal (endocytosis), often involving the trans-Golgi network/early

endosome (TGN/EE). Kinetics and steady-state localization differs for individual RK

species (5, 6). Until recently, there was only very limited insight into what happens to

PRKs in plant cells upon the arrival of the signal: that is, after specific ligand binding

resulting in an intracellular kinase domain activation and signaling initiation. Two side-by-

side reports in PNAS (7, 8) show that three different PRKs [PEP receptor 1 (PEPR1), EF-

TU RECEPTOR (EFR), and FLAGELLIN SENSING 2 (FLS2)], involved in biotic defense

interactions activated by three different ligands, are all removed from the cell surface via

clathrin-mediated endocytosis (CME). An interacting coreceptor, BRI1-ASSOCIATED

KINASE 1 (BAK1), is necessary for the internalization of all these activated receptors.

Requirement for the active RK domain was demonstrated for the FLS2 PRK, but this …

Zhang, H., Zhao, T., Zhuang, P., Song, Z., Du, H., Tang, Z., & Gao, Z. (2016). NbCZF1,

a novel C2H2-type zinc finger protein, as a new regulator of SsCut-induced plant

immunity in Nicotiana benthamiana. Plant and Cell Physiology, pcw160.

https://doi.org/10.1093/pcp/pcw160

SsCut, which functions as an elicitor, can induce plant immunity. In this study, we

utilized Nicotiana benthamiana and virus-induced gene silencing to individually decrease

the expression of over 2,500 genes. Using this forward genetics approach, several genes

were identified that, when silenced, compromised SsCut-triggered cell death based on a

cell death assay. A C2H2-type zinc finger gene was isolated from N. benthamiana.

Sequence analysis indicated that the gene encodes a 27-kDa protein with 253 amino

acids containing two typical C2H2-type zinc finger domains; this gene was named

NbCZF1. We found that SsCut-induced cell death could be inhibited by virus-induced

gene silencing of NbCZF1 in N. benthamiana. In addition, SsCut induces stomatal

closure, accompanied by reactive oxygen species (ROS) production by NADPH oxidases

and nitric oxide (NO) production. NbCZF1-silenced plants showed impaired SsCut-

induced stomatal closure, decreased SsCut-induced production of ROS and NO in guard

cells, and reduced SsCut-induced resistance against Phytophthora nicotianae. Taken

together, these results demonstrate that the NbCZF1-ROS-NO pathway mediates

multiple SsCut-triggered responses, including stomatal closure, hypersensitive responses,

and defense-related gene expression. This is the first report describing the function of a

C2H2-type zinc finger protein in N. benthamiana.

Zine, H., Rifai, L. A., Faize, M., Bentiss, F., Guesmi, S., Laachir, A., … Koussa, T. (2016).

Induced resistance in tomato plants against Verticillium wilt by the binuclear nickel

coordination complex of the ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole. Journal of

Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.6b00151

The ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole (L) and the complex bis [?-2,5-

bis(pyridin-2-yl)-1,3,4-thiadiazole-?4N2,N3:N4,N5] bis [dihydrato-?O) Nickel(II)]

tetrachloro trihydrate [Ni2L2(H2O)4]Cl4·3H2O (Ni2L2) were tested as inducers of plant

defenses and for their ability to protect tomato seedlings against verticillium wilt. In the

greenhouse they protected tomato seedlings against V. dahliae when they were applied

twice as foliar sprays at 100 ?g mL-1. A synergistic effect was observed between the

ligand L and the transition metal Ni as disease incidence was reduced by 38% with L and

by 57% with Ni2L2.Verticillium wilt foliar symptoms and vascular browning index were

reduced by 82% for L and by to 95% for Ni2L2. This protection ability was associated

with the induction of an oxidative burst and the activation of total phenolic content as

well as potentiation of the activity of peroxidase and polyphenol oxidase. These results

demonstrated that L and Ni2L2 can be considered as new activators of plant defenses

responses.